Hi Dave. I LOVE your Videos here. I think I know what Digikey's "mistake" is. You have got 4 Channels but inside you have only ONE Converter. So it converts the first input, then the second and so on. If you have 4 Converters they would convert all 4 Inputs at the same time. Its the same with the PICs. The 8bit PICs have ONE ADC but many Channels which you have to choose in your Registers.
You said the shunt are expensive but Farnell or Digikey has some nice ones. Ohmite make cheap Kelvin shunts 10 mOhm to 50 mOhm, 0.5 %, 50 ppm/C, 0.5 W - 1 W several types. Search for LVK12, LVK20 or LVK24.
You get lower drop, no problem, just select MAX4080T with higher gain and it's all good. Or put pair of 50 mOhm shunts in series :)
Next, Microchip also does some cheap precision dual opamps, MCP60x2. For the low offset one, if someone really needs PDIP, there is TC7650 with 5 uV max offset.
Sorry I had to check what gilding the lilly meant - according to urban dictionary:Gilding the Lilly- To adorn unnecessarily something already beautiful. The expression is a condensation of Shakespeare's metaphor in King John: "To gild refined gold, to paint the lily ... is wasteful and ridiculous excess." i.e. So basically what you mean there Dave - you "tarted up" your desisgn in places. that expression is a corker - it putting it straight in me lexicon :)
Hey Dave, first off im loving the project, and i can't wait to see how it turns out.
I was thinking about the MOSFET on resistance, that needed to be under 1.25*10^-3 ohms, how about adding two MOSFETS in serial thus lowering the overall resistance, or atleast making it an option on the board, so it could be soldered in if needed.
@EEVblog I bet the transformer makes up half of the price for the entire supply. By the way, which enclosure are you going to use? Try to be as international as possible (avoid jiffy boxes if they are not available internationally).
I've been following the "PSU" line of episodes closely 'cause I was in the market (the DIY market that is) for a nice PSU for my lab.
So I was wondering if you have plans to release a ready-made PCB kit for the thing.
Also I'd very much like to see a version of the schematic without the external ADC / DAC and the μCurrent functionality. I'd trade the lower complexity + cost for the added resolution and accuracy. (I'd also bet I'm not the only one)
@billysgeo The external ADC/ADC and uCurrent doesn't actually add a huge amount to the final BOM cost, you'd be surprised how much all the other stuff adds up to be.
Hi Dave are you going to sell this as complete kit or a fully assembled device once the design development is finished? I appreciate that this might a month or two away at a minimum.
i love how this series ended up its awesome Dave! i was checking parts here in my country wouldn't cost over 12 euros without transformer "i love it" "beauty" :)
I have one question: would it be possible to improve gain in opamp that sets voltage from 5 to 6, to get 12V on the output. Is this just trivial task (changing R29, R14-R16), or would i have to change a lot of other components?
I like that you did get rid of that current led opamp from the previous design, that one was a bad call.
But if you are worried about burden voltage on that mosfet shunt, why are you not referencing negative side of your output voltage divider for measurement on drain of that mosfet micro current shunt?
I hope your micro will do some out. voltage correction based on these measurements anyway...
@zega74 It remains an open design if it can be easily recreated in another medium. Dave's been gracious enough to share his entire schematic with us, and who knows how many hours of work he's put into all of this (engineering, taping, building, coding, etc.).
Still, I can take his design and recreate it in EAGLE, DEX, TINA, Multisim, DesignSpark, DipTrace, or any of the other odd-number of 'free' ECAD packages. Nothing is lost; IMO, open-source ECAD packages just aren't done cooking yet.
@SigEpBlue @zega74 Yes, Altium. It's the package I've been using for 20+ years. I have not learned another package sufficiently yet. It's still an open design if Altium is used. What if I did it in Eagle like 90+ % of other "open" hardware designs? You'd have to actually pay $800 or so for the full package of Eagle just to do this size board.
I was just kidding, give out gerbers at the end and you can lock it!
I am also pretty novice in KICAD so i understand your reluctance, and also having access to such a nice peace of SW like Altium designer, i would not switch SW!
Just make it at least 12 or 15 volts, 10 and some is such a odd value...
Oh and adding function buttons (memories for preset programmable voltage values) are the best, try to implement that, I never liked fiddling on power supply pot. to fine tune Vo.
I use a 6pin connector and an FTDI TTL-232R-5V USB-to-serial cable on all my designs now. It's a small investment to buy the cables, but it pays off because it's really easy to add UART access to a design plus you can standardise the "debug" port on everything and it doesn't add much to the BOM.
I apologise if someone has already suggested it (a quick scan showed me another person as thought about it), but you can reduce your pin count a little by using a I2C Port Expander such as the MCP23008 ($0.78 ea. in 100 qty) to drive the buttons and a few of the other non timing sensitive inputs/outputs. Or to reduce the need for a more expensive LCD module (but means more time is spent writing software), a 16-bit port Expander such as the MCP23017 ($0.91 ea. in 100 qty) could be used.
Why do you restrict yourself to DIP packages? They're a real pain to solder and you've got almost no chance of removing one from a plated through hole PCB.
I reckon a SOIC is much easier to solder (even for a beginner) and you have a chance of removing it if there's a problem.
@ArtistEngineer You've got to be kidding. Through hole packages are the easiest of all packages to solder. You shouldn't really have a problem removing a DIP package from a plated through hole unless there are pads on the component side of the board. Using chip holders eliminates this problem.
@spuzzdawg I've designed and hosted soldering workshops for novices. I found there were far less soldering faults on SMD boards than on through hole boards. Main source of faults are usually dry joints, which are almost non-existent with SMD. Add in the fact that you don't have to flip the board all time, and faults caused by parts moving are eliminated. My students used $15 Jaycar irons to solder SOIC and 1206 parts and they finished the task in half the time it took for the through hole board.
@spuzzdawg Are you saying that it's easier to solder, say, a 1206 resistor versus a thru-hole resistor? Take in to account bending the legs, pushing them through the holes, flipping the PCB over, heating and soldering the whole leg of the resistor (making sure you don't get a dry joint), waiting for the solder to harden, and then snipping off the leg. Compare that to soldering a single SMD resistor ... in fact, you could have soldered several resistors in the time it took to do one thru-hole!
Would it make sense to connect the LM334 to a negative voltage (maybe using a 7660) to get the output voltage completely down to zero in no-load condition?
Isn't hindsight great? I think looking back on it, it might have been better to use a 40-pin controller, which would allow a cheap parallel LCD and more control buttons. It might be time to invest in an A3 printer too :) I can't wait to see the time lapse PCB creation!
With the resistors, using identical parts in the feedback loops means they track both with tempco and with value. 0.1% resistors from the same batch and make at the same time are likely to match to better than 0.01%. Even 5% parts will match to 1% if used that way. Silicon resistors are always done that way, 30% tolerance and horrible tempco, but matching is perfect if you have similar dissipation across the chip.
Internal converters only will give 12 bits if you put the processor to sleep during the conversion. You have to buffer all output leads as well or you will get ground bounce from led current.Add that and the ext converter is looking easier from both cost and software complexity. i worked with 12 bit converters designed in the 1960's. Took 3 cards to implement the analogue side, and used lots of Intersil parts. Did do a stable 12 bits though.
Dave if I could make a suggestion, fix the LED/RST issue by putting a jumper in there. Kind of hackish, but also very experimenter friendly. And cheap. And easy.
@herctrap Easier and cheaper to use an external FT232. That way people that don't need the functionality don't have to pay for it, and there isn't a fiddly QFP for builders to solder.
Very thorough job! I'm glad that rift between you and Microchip seems to have fully healed. ;)
I went the 'easy route' for current measurement, using (three) TI INA226 in my supply design. 16-bit ADC, I2C, on-board current, voltage, and power registers, etc.
Other than that, it is SCARY, Dave, how closely our designs' functionality are to one another. Although I suppose there's only so many ways to make a wheel.... :)
Since this looks like it will be a kit, would it be possible to have the final PCB newbie friendly? The schematic looks quite busy, and it would be magnificent to possibly have the PCB silkscreened with boxes around each functional area on the PCB (i.e., voltage reference area, microcontroller and associated parts, etc.).
The motivation being that there are plenty of PSU designs out there, along with kits, but we're all taking baby steps with you through this design. :)
Hi Dave! I was wondering if mby it has come time to make another 50 and 100 $ meter shootout? But this time without wasting time on useless garbage and focus on new Extech and Amprobe offerings? I'm interested in ex 230 , mn47 and AM 270. These three look decent, would be interesting to see if extech and amprobe havelearned from it's mistakes (construction and dumb layout wise ) .
I love videos like this where you show the whole design process. The power supply looks really good too. Perhaps a bit over-engineered, but it doesn't cost a whole lot more as far as I can tell. Keep up the good work, Dave. :)
If the price overrun is a real concern then couldn't you pare back the frills a bit. The uCurrent feature is "nice" but unnecessary. If you can find the extra pins then you could use a cheaper LCD. I like the suggestion to cut the chip count by finding a micro with suitable DAC and ADC onboard.
I think it is a fine design and I like they way you are explaining your thought processes. I am not an EE an whilst I like the concept I don't see myself needing such a sophisticated piece of kit.
Could you explain why the DAC-D, CK and CS pins are 'fixed'? Is this a PCB type decision (like pin-out kind of things)? Because, in that situation you'd have to use software SPI anyway, as MISO is an input for the AVR, and DAC-D needs to be an output there.
Also the search on digikey with 4 converters is explained that digikey doesn't allow you to search for no. of inputs, but number of converters actually in the chip. Those with 4 converters in there can take 4 samples at once, simultaneously
@PonguigPeopinn Dave designed a Lab Power Supply and went through each step has he did it. Watch previous videos to before this one otherwise you will be lost.
Hi Dave, you have connected RESET pin to LED, so you have to disconnect it by fusebit. That means that you cannot use standard ISP for programming. You need to use High Voltage Parallel Programming (HVPP) or (HVSP) for serial.
@EEVblog Programming a bootloader and then flashing the firmware via RS232 might be an option. So first of all you programm the bootloader and firmware via ISP. Then configure the reset pin as an i/o pin (programming via isp will not work anymore). For further firmware- updates, you use RS232 and the bootloader. I will recommend to programm the avr via isp on a separate programming jig. So you have the option to use the ISP dedicated Pins PB3, PB4, PB5 as individual I/O pins.
@wxing I think it'd gobble up a LOT of time on AD conversion when it could be doing other things. An external solution is faster, less-noisy, probably more accurate, and no mucking about in software to make it play nice, e.g. low power mode for noise reduction. :) Just my $0.02.
AWESOME as allways Dave! Can't wait to see the other videos! And by the way that heatsink thing is really a trap for young players!!, and I fell into that a couple of times. Hopefully after scratching my head for a while, I realized my mistake and put some insulator washers and that silica thing to keep it from shortening...you know how that goes...."fuckup and learn"...of course, then you change it to "Fortune and glory, kid. fortune and glory" :)
Dave did you consider dsPIC33FJ64GP802 : it has 14bit DAC, 12bit ADC, available in DIP 28 package and costs around $4. Having 3 chips in one should reduce the cost of the kit.
@starlino I look a look at that very interesting device. Was considering that because the DAC is designed for audio purposes, wondering if it could pose a problem. The datasheet states that each channel needs a stream of data else they will load with a single default value... could be a headache. Also states some other internal circuitry, but didn't look into it.
@starlino Won't that mess up the Arduino compatibility? I think many people appreciate being able to use that programing environment to mod the kit. Other than that, nice suggestion!
@silverstream314 nothing says that open source means Atmel only, The way I see it Open Source means also to be Open-Minded, choose best component for the job. MPLAB is free, then you have peguino , however the no-cost C30 version is only limited by lack of optimization which is not critical in 99% of projects.
@starlino I said nothing about open source, I was talking about the arduino compatibility specifically. It is by far the most common programming environment for microcontrollers for beginners, and thus I think it is a good idea to use it.
@starlino The problem with moving to that chip is that the pin requirements become harder. He's trying to reduce the number of pins currently, while it would reduce the part count, it introduces new problems, mainly replacing 5 pins to drive the SPI to 4 12-bit ADC pins and 2 12-bit DAC pins. I know the current schematic is showing that he's using 8 pins, but he states he wants to use a ceramic osc. There is work around though such as using a I2C port expander (comment coming soon).
I just have to say that you have designed an amazing power supply and I cannot wait for further posts on it. Every aspect is appealing. I was considering getting a bench-top power supply as a component for my lab but to work off of this design would be amazing. Can't wait for future videos.
On a side note, it was interesting that Digi-Key listed the ADC converter count but not the actual channel count. Understandably there was few 4-converter ADCs as most contain only a single converter and s/h.
Hi Dave, isn't the design lacking some bulk capacitance?
Also, the uCurrent bypass fet has its gate at Vin, this means even the smallest spike above 20V will kill this mosfet. Maybe add a 10-15V zener there. The uCurrent amp terminal goes directly to the outside world, ESD anyone?
Any idea about the LT3080's capability of surviving Vout > Vin (for example with a battery or braking motor connected)? My impression is that it cannot handle it, so perhaps a good idea to add an antiparallel diode.
Nice looking power supply. I designed and built one about 20 to 25 years ago when I was just learning electronics. I opened it up not too long ago and and was amazed that it never burned my house down! LOL. There's no fuse on the mains and no heat sink on the regulator.
I still use it but need to built another now that I'm out of the "know enough to be dangerous" phase.
Absolutely awesome Dave. As a newbie most of this goes over my head but slowly and surely some of it is beginning to stick. I've equipped my workshop with most of your suggestions from an earlier vid but I can't wait to have a go at this. Hurry with the next chapter!!!! All the best to you and yours. Hope 2012 is great for you.
is there any chance to use RGB backlight on that LCD screen to indicate if everything is OK(green backlight) or PSU is overloaded(red or blinking red backlight)? that would be awesome indication.
My attention may have slipped, or my memory faded, but why not have it go up to 12V wich is a pretty standard value? I might buy a kit from you if the price is right, and piggy back it to my crude but grunty supply. It would be nice with a precision one!
I have a feeling if I get one of these kits that I'm going to mod the RGB back light to change on the current, red for highest, green for lowest, ect :P. Also gah surface mount, I suppose I need some practice anyway.
@DaemonPanda Yeah, considered that, and actually had it on an early draft with another LCD using novel mounting, but just went with a LED on the front panel instead. Free micro pins is an issue.
@EEVblog I once got rid of a similar problem by recording the noise and inverting it, then pasting this with the audio to cancel the noise. Might work, might not!
@EEVblog quite possible, sounds like some digital artifact. The parts where you are talking about Digikey and the LCD are artifact free. Its nothing major, and you can be heard clearly, but it is a bit distracting.
As for the video itself: I like it! Can't wait to see the next video!
No Digi-Key FAIL at all: there are separate columns for the number of ADC *converters* vs the number of *channels*. Most ADCs with multiple channels still only have one converter, and the same goes for microcontrollers.
Amaizing to see a proffesional engineer doing his job and seeing the end result. Dave thanks so much for this mini series, I've learned much from them. But howbout' sharing the schematic with teh internet ? :)
@pisnahuj10 What's a "hobbyist" price. The case costs money, the LCD costs money, the heatsink costs money, the PCB and all the other parts cost money. It all ads up. This one does cost more than intended though...
..with an external supply, some reverse polarity protection might be a good idea...
Another issue is that the external mains PSU should have some weak coupling (e.g. 10-100K + 10-100nf in parallel) between its negative output and mains earth - you don't want a hard connection to avoid melting scope probe ground leads, but you also don't want the output floating at half mains, which is what you tend to get from non-earthed PSUs.
i don't know what is happening 90% of the time, but i enjoy electronics and fascinated by how they work, so i always really enjoy your videos. keep it up!
why dont you repalce the 1R resistor with a lower value like a 0.1R one?
Yaga19 2 weeks ago
I still don't understand the shunt resistor part.
oash82 1 month ago
Hi Dave. I LOVE your Videos here. I think I know what Digikey's "mistake" is. You have got 4 Channels but inside you have only ONE Converter. So it converts the first input, then the second and so on. If you have 4 Converters they would convert all 4 Inputs at the same time. Its the same with the PICs. The 8bit PICs have ONE ADC but many Channels which you have to choose in your Registers.
rbsphoenix1 1 month ago
You said the shunt are expensive but Farnell or Digikey has some nice ones. Ohmite make cheap Kelvin shunts 10 mOhm to 50 mOhm, 0.5 %, 50 ppm/C, 0.5 W - 1 W several types. Search for LVK12, LVK20 or LVK24.
You get lower drop, no problem, just select MAX4080T with higher gain and it's all good. Or put pair of 50 mOhm shunts in series :)
Next, Microchip also does some cheap precision dual opamps, MCP60x2. For the low offset one, if someone really needs PDIP, there is TC7650 with 5 uV max offset.
Vlakpage 1 month ago in playlist More videos from EEVblog
@Vlakpage The Microchip opamps only go to 6V max.
EEVblog 1 month ago
Dave can I just say
You Fu$ken Rock.
Nice work. I love your vids.
TheJMan11000111 1 month ago
Sorry I had to check what gilding the lilly meant - according to urban dictionary:Gilding the Lilly- To adorn unnecessarily something already beautiful. The expression is a condensation of Shakespeare's metaphor in King John: "To gild refined gold, to paint the lily ... is wasteful and ridiculous excess." i.e. So basically what you mean there Dave - you "tarted up" your desisgn in places. that expression is a corker - it putting it straight in me lexicon :)
raindogred 1 month ago
Dave, I love this design! I would buy a kit when you have it finalized. Looking forward to the final videos. Keep up the great work and videos!
Kryoclasm 2 months ago
Hey Dave, first off im loving the project, and i can't wait to see how it turns out.
I was thinking about the MOSFET on resistance, that needed to be under 1.25*10^-3 ohms, how about adding two MOSFETS in serial thus lowering the overall resistance, or atleast making it an option on the board, so it could be soldered in if needed.
Well thats my 2 cents, all the best from denmark.
fuba44 2 months ago
@EEVblog I bet the transformer makes up half of the price for the entire supply. By the way, which enclosure are you going to use? Try to be as international as possible (avoid jiffy boxes if they are not available internationally).
ivaneduardo747 2 months ago
Hay Dave,
I've been following the "PSU" line of episodes closely 'cause I was in the market (the DIY market that is) for a nice PSU for my lab.
So I was wondering if you have plans to release a ready-made PCB kit for the thing.
Also I'd very much like to see a version of the schematic without the external ADC / DAC and the μCurrent functionality. I'd trade the lower complexity + cost for the added resolution and accuracy. (I'd also bet I'm not the only one)
Thank you once again! Keep it up!
billysgeo 2 months ago
@billysgeo The external ADC/ADC and uCurrent doesn't actually add a huge amount to the final BOM cost, you'd be surprised how much all the other stuff adds up to be.
EEVblog 2 months ago
Hi Dave are you going to sell this as complete kit or a fully assembled device once the design development is finished? I appreciate that this might a month or two away at a minimum.
SuperMadpom 2 months ago
"Decided not to use the more expensive 10-turn potentiometers"
Head = exploded.
ixamraxi 2 months ago in playlist Uploaded videos
i love how this series ended up its awesome Dave! i was checking parts here in my country wouldn't cost over 12 euros without transformer "i love it" "beauty" :)
zox012 2 months ago
I have one question: would it be possible to improve gain in opamp that sets voltage from 5 to 6, to get 12V on the output. Is this just trivial task (changing R29, R14-R16), or would i have to change a lot of other components?
pikoliii 2 months ago
I like that you did get rid of that current led opamp from the previous design, that one was a bad call.
But if you are worried about burden voltage on that mosfet shunt, why are you not referencing negative side of your output voltage divider for measurement on drain of that mosfet micro current shunt?
I hope your micro will do some out. voltage correction based on these measurements anyway...
Is the SCH/PCB SW KICAD?
zega74 2 months ago
@zega74 Altium Designer
jmdejoanelli 2 months ago in playlist Power Supply Design
@jmdejoanelli
Altium,
So much about "open" hardware...
zega74 2 months ago
@zega74 It remains an open design if it can be easily recreated in another medium. Dave's been gracious enough to share his entire schematic with us, and who knows how many hours of work he's put into all of this (engineering, taping, building, coding, etc.).
Still, I can take his design and recreate it in EAGLE, DEX, TINA, Multisim, DesignSpark, DipTrace, or any of the other odd-number of 'free' ECAD packages. Nothing is lost; IMO, open-source ECAD packages just aren't done cooking yet.
SigEpBlue 2 months ago
@SigEpBlue @zega74 Yes, Altium. It's the package I've been using for 20+ years. I have not learned another package sufficiently yet. It's still an open design if Altium is used. What if I did it in Eagle like 90+ % of other "open" hardware designs? You'd have to actually pay $800 or so for the full package of Eagle just to do this size board.
EEVblog 2 months ago
@EEVblog
I was just kidding, give out gerbers at the end and you can lock it!
I am also pretty novice in KICAD so i understand your reluctance, and also having access to such a nice peace of SW like Altium designer, i would not switch SW!
Just make it at least 12 or 15 volts, 10 and some is such a odd value...
Oh and adding function buttons (memories for preset programmable voltage values) are the best, try to implement that, I never liked fiddling on power supply pot. to fine tune Vo.
zega74 2 months ago
In what program did You make that schematic?
kildas 2 months ago
@kildas Altium Designer
jmdejoanelli 2 months ago in playlist Power Supply Design
BTW, Why not share single SPI bus by ADC and DAC ? Only separate CS lines are required.
jpelczar 2 months ago
More PSU design vids please! I would love to see the board layout timelapse!
flubba86 2 months ago
@flubba86 51:05
jmdejoanelli 2 months ago in playlist Power Supply Design
I use a 6pin connector and an FTDI TTL-232R-5V USB-to-serial cable on all my designs now. It's a small investment to buy the cables, but it pays off because it's really easy to add UART access to a design plus you can standardise the "debug" port on everything and it doesn't add much to the BOM.
ArtistEngineer 2 months ago
Will you continue your power supply to PCB?
SajjadBro 2 months ago in playlist Power Supply Design
Dave ,I look forward to See PCB HOME MADE ,I would happy to see how properly it should be !?
podarbu 2 months ago
are you going to build it? or even set it up as a kit to buy?
puop 2 months ago
@puop He mentioned it will be a kit.
envisionelec 2 months ago
@envisionelec sweet deal... I must have missed that part of the video lol ooo ADD got me again
puop 2 months ago
I apologise if someone has already suggested it (a quick scan showed me another person as thought about it), but you can reduce your pin count a little by using a I2C Port Expander such as the MCP23008 ($0.78 ea. in 100 qty) to drive the buttons and a few of the other non timing sensitive inputs/outputs. Or to reduce the need for a more expensive LCD module (but means more time is spent writing software), a 16-bit port Expander such as the MCP23017 ($0.91 ea. in 100 qty) could be used.
crenn6977 2 months ago
Man, DaveCAD got pretty sophisticated looking!
dylanpalmediy 2 months ago
Great series, I'm planning to make my own version using an STM32 which has 12bit DAC/ADC with some cheap seven segment display modules
BadgerInverted 2 months ago in playlist Uploaded videos
Optical vs mechanical rotary encoder. What was the design decision there?
ArtistEngineer 2 months ago
Why do you restrict yourself to DIP packages? They're a real pain to solder and you've got almost no chance of removing one from a plated through hole PCB.
I reckon a SOIC is much easier to solder (even for a beginner) and you have a chance of removing it if there's a problem.
ArtistEngineer 2 months ago
@ArtistEngineer You've got to be kidding. Through hole packages are the easiest of all packages to solder. You shouldn't really have a problem removing a DIP package from a plated through hole unless there are pads on the component side of the board. Using chip holders eliminates this problem.
spuzzdawg 2 months ago
@spuzzdawg I've designed and hosted soldering workshops for novices. I found there were far less soldering faults on SMD boards than on through hole boards. Main source of faults are usually dry joints, which are almost non-existent with SMD. Add in the fact that you don't have to flip the board all time, and faults caused by parts moving are eliminated. My students used $15 Jaycar irons to solder SOIC and 1206 parts and they finished the task in half the time it took for the through hole board.
ArtistEngineer 2 months ago
@spuzzdawg Are you saying that it's easier to solder, say, a 1206 resistor versus a thru-hole resistor? Take in to account bending the legs, pushing them through the holes, flipping the PCB over, heating and soldering the whole leg of the resistor (making sure you don't get a dry joint), waiting for the solder to harden, and then snipping off the leg. Compare that to soldering a single SMD resistor ... in fact, you could have soldered several resistors in the time it took to do one thru-hole!
PossumTucker 2 months ago
@spuzzdawg I agree with ArtistEngineer SMD is sooooo much quicker
jmdejoanelli 2 months ago
Would it make sense to connect the LM334 to a negative voltage (maybe using a 7660) to get the output voltage completely down to zero in no-load condition?
ondre2k 2 months ago in playlist Uploaded videos
Isn't hindsight great? I think looking back on it, it might have been better to use a 40-pin controller, which would allow a cheap parallel LCD and more control buttons. It might be time to invest in an A3 printer too :) I can't wait to see the time lapse PCB creation!
Zadster 2 months ago
With the resistors, using identical parts in the feedback loops means they track both with tempco and with value. 0.1% resistors from the same batch and make at the same time are likely to match to better than 0.01%. Even 5% parts will match to 1% if used that way. Silicon resistors are always done that way, 30% tolerance and horrible tempco, but matching is perfect if you have similar dissipation across the chip.
SeanBZA 2 months ago
Internal converters only will give 12 bits if you put the processor to sleep during the conversion. You have to buffer all output leads as well or you will get ground bounce from led current.Add that and the ext converter is looking easier from both cost and software complexity. i worked with 12 bit converters designed in the 1960's. Took 3 cards to implement the analogue side, and used lots of Intersil parts. Did do a stable 12 bits though.
SeanBZA 2 months ago
Fantastic Dave!!! Waiting time laps of PCB design :)
TheLaidukas 2 months ago
I would keep it simple. use pwm and DA in the micro, if higher precision is needed then dither. but I think the pwm already does 16bit.
and I would do switchmode.. linear is terrible. it's weak and it's super inefficient.
microamp is a nice feature though.
DanFrederiksen 2 months ago
I hate waiting for the next video! :)
Milten130 2 months ago
Dave if I could make a suggestion, fix the LED/RST issue by putting a jumper in there. Kind of hackish, but also very experimenter friendly. And cheap. And easy.
mausball 2 months ago
why dont you add also the ft232
it would be nice to have dataloging on the PC
-------------------
also it would be easier to use the hardware interupts for the rotary encoders
herctrap 2 months ago
@herctrap Easier and cheaper to use an external FT232. That way people that don't need the functionality don't have to pay for it, and there isn't a fiddly QFP for builders to solder.
Zadster 2 months ago
@Zadster
Not the ft232 - but an unpopulated SSOP-28 with an unpopulated USB connector
and the CN3
herctrap 2 months ago
Dave, should you take care about the max Vgs (+-20V) of Q4?
tictourette 2 months ago
@tictourette I'm fairly certain he's aware of this. You know - as a professional design engineer. ;)
envisionelec 2 months ago
Very thorough job! I'm glad that rift between you and Microchip seems to have fully healed. ;)
I went the 'easy route' for current measurement, using (three) TI INA226 in my supply design. 16-bit ADC, I2C, on-board current, voltage, and power registers, etc.
Other than that, it is SCARY, Dave, how closely our designs' functionality are to one another. Although I suppose there's only so many ways to make a wheel.... :)
SigEpBlue 2 months ago
Dave,
Since this looks like it will be a kit, would it be possible to have the final PCB newbie friendly? The schematic looks quite busy, and it would be magnificent to possibly have the PCB silkscreened with boxes around each functional area on the PCB (i.e., voltage reference area, microcontroller and associated parts, etc.).
The motivation being that there are plenty of PSU designs out there, along with kits, but we're all taking baby steps with you through this design. :)
sabamacx 2 months ago
I love the openhardware logo. Nice!
Rubdos 2 months ago
Hello Dave!
Why you dont used a I²C Port expander for the buttons so u can use them for other stuff?
but realy nice project! :-)
schimpl94 2 months ago
Hi Dave! I was wondering if mby it has come time to make another 50 and 100 $ meter shootout? But this time without wasting time on useless garbage and focus on new Extech and Amprobe offerings? I'm interested in ex 230 , mn47 and AM 270. These three look decent, would be interesting to see if extech and amprobe havelearned from it's mistakes (construction and dumb layout wise ) .
pisnahuj10 2 months ago in playlist Uploaded videos
Gild the lily - To apply unnecessary ornament - to over embellish.
uGateKiller 2 months ago
I love videos like this where you show the whole design process. The power supply looks really good too. Perhaps a bit over-engineered, but it doesn't cost a whole lot more as far as I can tell. Keep up the good work, Dave. :)
TheCrazyInventor 2 months ago 17
If the price overrun is a real concern then couldn't you pare back the frills a bit. The uCurrent feature is "nice" but unnecessary. If you can find the extra pins then you could use a cheaper LCD. I like the suggestion to cut the chip count by finding a micro with suitable DAC and ADC onboard.
I think it is a fine design and I like they way you are explaining your thought processes. I am not an EE an whilst I like the concept I don't see myself needing such a sophisticated piece of kit.
Wilfredkazoks 2 months ago
Awesome again Dave!!!
ntjbjhq 2 months ago
That is some serious gilding of lilles:)
Nermash 2 months ago
Could you explain why the DAC-D, CK and CS pins are 'fixed'? Is this a PCB type decision (like pin-out kind of things)? Because, in that situation you'd have to use software SPI anyway, as MISO is an input for the AVR, and DAC-D needs to be an output there.
Also the search on digikey with 4 converters is explained that digikey doesn't allow you to search for no. of inputs, but number of converters actually in the chip. Those with 4 converters in there can take 4 samples at once, simultaneously
nlhans1990 2 months ago
@nlhans1990 They aren't fixed, that's a leftover on the schematic I didn't clean up. Yes, software SPI.
EEVblog 2 months ago
Comment removed
nlhans1990 2 months ago
Comment removed
mvdswaluw 2 months ago
Can someone explain to me wtf this is, exactly and concisely?
PonguigPeopinn 2 months ago in playlist Uploaded videos
@PonguigPeopinn Dave designed a Lab Power Supply and went through each step has he did it. Watch previous videos to before this one otherwise you will be lost.
GoneBadKiwi 2 months ago
@PonguigPeopinn Start from part 1!
sabamacx 2 months ago
Very nice, thanks for making the informative series Dave! I think I'll buy a kit when they're finished!
DjViOd 2 months ago in playlist Power Supply Design
Guild the lilly & get a computer for the lab.
heroineworshipper 2 months ago in playlist Uploaded videos
Hi Dave, you have connected RESET pin to LED, so you have to disconnect it by fusebit. That means that you cannot use standard ISP for programming. You need to use High Voltage Parallel Programming (HVPP) or (HVSP) for serial.
snik2pl 2 months ago
@snik2pl Yeah, I only just found that out. That limitation kinda sucks...
EEVblog 2 months ago
@EEVblog
You can use buttons PB1, PB2, PB3, PB4 with R-2R resistor ladder and internal atmega ADC to decode pressed button. This will give you 3 extra pin.
snik2pl 2 months ago 9
Comment removed
jmdejoanelli 2 months ago in playlist Power Supply Design
@EEVblog Programming a bootloader and then flashing the firmware via RS232 might be an option. So first of all you programm the bootloader and firmware via ISP. Then configure the reset pin as an i/o pin (programming via isp will not work anymore). For further firmware- updates, you use RS232 and the bootloader. I will recommend to programm the avr via isp on a separate programming jig. So you have the option to use the ISP dedicated Pins PB3, PB4, PB5 as individual I/O pins.
TheElectr0nicus 2 months ago
Comment removed
TheElectr0nicus 2 months ago
Why did you use a separate ADC instead of the one built in the Atmega?
ultimatefang007 2 months ago
@ultimatefang007 12bit resolution instead of 10bit.
EEVblog 2 months ago
@EEVblog
Could internal AVR ADC be used in this project when ADC resolution enhanced by overlampling? this can give up to 16 bit resolution or even more
Downside - lower sampling frequency (for 12bits - 16x slower) and the need to include PWM noise to input signal
wxing 2 months ago
@wxing I think it'd gobble up a LOT of time on AD conversion when it could be doing other things. An external solution is faster, less-noisy, probably more accurate, and no mucking about in software to make it play nice, e.g. low power mode for noise reduction. :) Just my $0.02.
SigEpBlue 2 months ago
@ultimatefang007 He spent like 5 mins talking about that exact question. You should watch the entire video :)
jmdejoanelli 2 months ago in playlist Power Supply Design
AWESOME as allways Dave! Can't wait to see the other videos! And by the way that heatsink thing is really a trap for young players!!, and I fell into that a couple of times. Hopefully after scratching my head for a while, I realized my mistake and put some insulator washers and that silica thing to keep it from shortening...you know how that goes...."fuckup and learn"...of course, then you change it to "Fortune and glory, kid. fortune and glory" :)
sgajate 2 months ago
What if you use the LCD backlight for status? Display goes red when you go into current limit, green when you're not, yellow when you're at 90% load.
therealjammit 2 months ago
circuit wasn't drawn in good ole' DaveCAD.. do not want..
kiyotewolf 2 months ago
Dave did you consider dsPIC33FJ64GP802 : it has 14bit DAC, 12bit ADC, available in DIP 28 package and costs around $4. Having 3 chips in one should reduce the cost of the kit.
starlino 2 months ago
@starlino Didn't catch that one, I only found a 40pin DIP 24F chip I think. Will have to investigate, thanks.
EEVblog 2 months ago
@starlino Don't know where you saw that, but at farnell it's twice that.
ultimatefang007 2 months ago
@ultimatefang007 dsPIC33FJ64GP802-I/SP - mouser.com has it at $4.06 (x 100 )
starlino 2 months ago
@starlino I look a look at that very interesting device. Was considering that because the DAC is designed for audio purposes, wondering if it could pose a problem. The datasheet states that each channel needs a stream of data else they will load with a single default value... could be a headache. Also states some other internal circuitry, but didn't look into it.
DarkInsanePyro 2 months ago
@starlino Maybe if you live in the US it's that convenient. For shipping to europe they charge 50 bucks. Not cool.
ultimatefang007 2 months ago
@starlino Won't that mess up the Arduino compatibility? I think many people appreciate being able to use that programing environment to mod the kit. Other than that, nice suggestion!
silverstream314 2 months ago
@silverstream314 nothing says that open source means Atmel only, The way I see it Open Source means also to be Open-Minded, choose best component for the job. MPLAB is free, then you have peguino , however the no-cost C30 version is only limited by lack of optimization which is not critical in 99% of projects.
starlino 2 months ago
@starlino I said nothing about open source, I was talking about the arduino compatibility specifically. It is by far the most common programming environment for microcontrollers for beginners, and thus I think it is a good idea to use it.
silverstream314 2 months ago
@starlino The problem with moving to that chip is that the pin requirements become harder. He's trying to reduce the number of pins currently, while it would reduce the part count, it introduces new problems, mainly replacing 5 pins to drive the SPI to 4 12-bit ADC pins and 2 12-bit DAC pins. I know the current schematic is showing that he's using 8 pins, but he states he wants to use a ceramic osc. There is work around though such as using a I2C port expander (comment coming soon).
crenn6977 2 months ago
owesome
ArunaRubasinghe 2 months ago
you are amazing dave! when are you going to start your own company!
realcomix1 2 months ago
I just have to say that you have designed an amazing power supply and I cannot wait for further posts on it. Every aspect is appealing. I was considering getting a bench-top power supply as a component for my lab but to work off of this design would be amazing. Can't wait for future videos.
On a side note, it was interesting that Digi-Key listed the ADC converter count but not the actual channel count. Understandably there was few 4-converter ADCs as most contain only a single converter and s/h.
DarkInsanePyro 2 months ago
Hi Dave, isn't the design lacking some bulk capacitance?
Also, the uCurrent bypass fet has its gate at Vin, this means even the smallest spike above 20V will kill this mosfet. Maybe add a 10-15V zener there. The uCurrent amp terminal goes directly to the outside world, ESD anyone?
Any idea about the LT3080's capability of surviving Vout > Vin (for example with a battery or braking motor connected)? My impression is that it cannot handle it, so perhaps a good idea to add an antiparallel diode.
AnnoyingVerification 2 months ago
Absolutely magnificent Dave, you have outdone yourself!
sabamacx 2 months ago
Why did you decide against using the hardware SPI for both ADC and DAC?
MrP00f 2 months ago
@MrP00f I was thinking about using MC14053 to allow in-system programming with DAC soldered. Also, an SMD-only version would be nice ;)
jpelczar 2 months ago
This looks and feels professional.
You got yourself another subscriber.
ElectricSparq 2 months ago
Will there be a kit ? else i have to custom design the pcb and manufacture it in china :P
spikeguns1 2 months ago
What software are you using to make the schematic?
mathtek1 2 months ago
@mathtek1
Altium Designer
michaelnjensen 2 months ago
Nice looking power supply. I designed and built one about 20 to 25 years ago when I was just learning electronics. I opened it up not too long ago and and was amazed that it never burned my house down! LOL. There's no fuse on the mains and no heat sink on the regulator.
I still use it but need to built another now that I'm out of the "know enough to be dangerous" phase.
TerminalJack505 2 months ago
Absolutely awesome Dave. As a newbie most of this goes over my head but slowly and surely some of it is beginning to stick. I've equipped my workshop with most of your suggestions from an earlier vid but I can't wait to have a go at this. Hurry with the next chapter!!!! All the best to you and yours. Hope 2012 is great for you.
rotlerin 2 months ago
is there any chance to use RGB backlight on that LCD screen to indicate if everything is OK(green backlight) or PSU is overloaded(red or blinking red backlight)? that would be awesome indication.
rzkrr 2 months ago
You should make your own EEVBlog Title block for Altium
lexxmac 2 months ago
Use the RGB back light as current overload indicator by switching from green or blue (user selectable) to red.
ornotermes 2 months ago
My attention may have slipped, or my memory faded, but why not have it go up to 12V wich is a pretty standard value? I might buy a kit from you if the price is right, and piggy back it to my crude but grunty supply. It would be nice with a precision one!
bonecrime 2 months ago
I have a feeling if I get one of these kits that I'm going to mod the RGB back light to change on the current, red for highest, green for lowest, ect :P. Also gah surface mount, I suppose I need some practice anyway.
DaemonPanda 2 months ago 8
@DaemonPanda Yeah, considered that, and actually had it on an early draft with another LCD using novel mounting, but just went with a LED on the front panel instead. Free micro pins is an issue.
EEVblog 2 months ago
@DaemonPanda Or you could use it to indicate when the current limiter is activated, etc, which could be pretty neat.
silverstream314 2 months ago
@EEVblog can you put up the schematic for download plz dave
mm5032 2 months ago
@mm5032 Done.
EEVblog 2 months ago
Can't wait for the kit :)
xXdenhartXx 2 months ago
Does anybody else notice some weird audio artifacts in this video?
MrP00f 2 months ago
@MrP00f If so, sorry. I used a noise removal algorithm on this one to get rid of the fan conditioning noise. Artifacts of that?
EEVblog 2 months ago
@EEVblog I once got rid of a similar problem by recording the noise and inverting it, then pasting this with the audio to cancel the noise. Might work, might not!
cjmitz 2 months ago
@EEVblog quite possible, sounds like some digital artifact. The parts where you are talking about Digikey and the LCD are artifact free. Its nothing major, and you can be heard clearly, but it is a bit distracting.
As for the video itself: I like it! Can't wait to see the next video!
MrP00f 2 months ago
No Digi-Key FAIL at all: there are separate columns for the number of ADC *converters* vs the number of *channels*. Most ADCs with multiple channels still only have one converter, and the same goes for microcontrollers.
gxti 2 months ago
@gxti Of course, so there is. Dave Fail.
EEVblog 2 months ago
how many years of school it take to have a EE diploma?
hitachi088 2 months ago
Will we see the finished power supply soon? It's looking good just from the schematic, maybe a little over-the-top tho.
CoolDudeClem 2 months ago
Amaizing to see a proffesional engineer doing his job and seeing the end result. Dave thanks so much for this mini series, I've learned much from them. But howbout' sharing the schematic with teh internet ? :)
pisnahuj10 2 months ago
@pisnahuj10 Or mby start selling it for a hobbyist price ;)
pisnahuj10 2 months ago
@pisnahuj10 What's a "hobbyist" price. The case costs money, the LCD costs money, the heatsink costs money, the PCB and all the other parts cost money. It all ads up. This one does cost more than intended though...
EEVblog 2 months ago
@EEVblog I'm not sure but anything under 150$ mark would be nice :)
pisnahuj10 2 months ago
..with an external supply, some reverse polarity protection might be a good idea...
Another issue is that the external mains PSU should have some weak coupling (e.g. 10-100K + 10-100nf in parallel) between its negative output and mains earth - you don't want a hard connection to avoid melting scope probe ground leads, but you also don't want the output floating at half mains, which is what you tend to get from non-earthed PSUs.
mikeselectricstuff 2 months ago
Dave uses opera? Awesome :D. Best browser out there.
DaemonPanda 2 months ago
@DaemonPanda No, I use Chrome mostly. Opera had less clutter for the video.
EEVblog 2 months ago
@EEVblog Ah okay, that'd explain the default look (ugly) Shame. I really like opera more than chrome and FF.
DaemonPanda 2 months ago
I like the shirt Dave. It looks like you're getting comfortable. Have fun, bud!
fingerboy18 2 months ago
i don't know what is happening 90% of the time, but i enjoy electronics and fascinated by how they work, so i always really enjoy your videos. keep it up!
chapman112 2 months ago 2
Looks really nice Dave I love the 5 Volt USB chargeing output. You have allot of nice little tutches in this project "I LOVE IT" hahahahahaha
g1fsh 2 months ago 7
@g1fsh There is one more thing in the design people haven't seen yet...
EEVblog 2 months ago
Nice design Dave. One little addition that would be nice would be a switched buzzer to go along with the the CC led.
smithyduk 2 months ago in playlist Power Supply Design
@smithyduk I originally wanted a buzzer, but forgot to include it in the final design - Doh!
EEVblog 2 months ago
yay!
gryzman 2 months ago
Finally!!!
Jprojects1 2 months ago