Experiments 4.3: Binary Coded Decimal (BCD) to 7 Segment Display Example

[LiMiTeDxStudios]

Whoops i thought this was a minecraft bcde to 7 seg tut

[Rekiem24]

Hi!

I was wondering if u could help me a little bit. I'm trying to do the same experiment as you with same components but when I plugg the 5v to work the 7-seg show me an eight, if I press the "a" shows me 9....bufff I'm stuck! Could be wrong conections in the breadboard? I'll send u a picture if u could have a look? please!

Thanks

[Leuel48fan]

is it possible to make it desplay the top segment when showing 6 and bottom segment when displaying 9?

[DerekMolloyDCU]

@Leuel48fan Missed this - no, not with the BCD->7 Segment display I am using. You would have to add additional circuitry when a BCD 0110 or 1001 is present and it could be quite messy.

[The1970sInfatuate]

What kind of push buttons are those? I'm building my own homemade powered breadboard and want to put momentary push buttons on it to use for manually toggling clock inputs and other things. I'm afraid the switches might create a short because the switches themselves have to be powered and grounded.

[DerekMolloyDCU]

@The1970sInfatuate They are just momentary push buttons, but you are right if you tie the output side of the switch to GND and the input side to +5V, when you press the button you will create a short. This is where a pull-down resistor comes in. A value of 10k or greater between the output side of the switch and GND will mean that when the button is pressed you are connecting the output side to +5V, without shorting the supply.

[The1970sInfatuate]

@DerekMolloyDCU Would there still be a short circuit if you use a pull-up resistor and send the voltage signal to the push button switch and to a load?  In school, I used normally closed push buttons with a 1kΩ pull-up resistor and had to power both the switch and the circuit load.

[DerekMolloyDCU]

@The1970sInfatuate Yes, these are normally open momentary push buttons. If the +5V is connected to one side of the resistor and the GND is connected to the other you will have a 5V drop over the resistor. A 1K resistor is a bit low as there will be a current flow through the resistor I=V/R = 5/1000 = 5mA. Bringing this to 10K reduces the current to 0.5mA. Do a google search for "pull up resistor" and check that you have wired your circuit the same way.

[The1970sInfatuate]

@DerekMolloyDCU It doesn't make any difference if there is a load? I'm not sure if there was any internal wiring in the breadboards I used back in college that would have prevented shorting. I know they were normally closed, and normally connected the load circuit to ground and the push button itself had to be powered by a 5V source through a 1kΩ resistor.

[BeatySword]

MY BRAIN HUUUUURTS!

[1jellymeow]

Hello...can you help me to do the connection by using the components below : 74LS138 x1 74LS574 x1 74LS541 x1 7 Segment common anode x1 Push button SW x2 Header pin 1x32ways x2 Resistor 330/220 x9 Resistor 10k/4.7k x2 7805 x1 0.1uF x2 10uF x1 LED x1 DC jack socket x1 Wire single core 1m Wires wrap 1m Solder lead 1m Extra components or mode can be added...TQ

[verrakten]

nice video

[alona0001]

how about adding two binary numbers? its possible ryt ? how could that be.. can you post tutorial sir. . thanks

[DerekMolloyDCU]

@alona0001 Yes, I plan to do a tutorial on adding binary numbers. Thanks for the reminder.

[alona0001]

@DerekMolloyDCU when wud it be . wud it be posiblr tomorrow ? haha anyways thanks for the reply sir :)

[0923rio]

hi sir! so far ur video is the best i've seen!....it's stedy...vivid video and ur explanation is clear..GREAT!! keep it up :) god speed.

[0923rio]

sir! how bout using 2 push button switches using 74ls04 and 74ls02?can u pls. share to me ur brilliant idea?... tnx :)

[DerekMolloyDCU]

@0923rio With 10 possible states the smallest number of buttons (n) we can use is the 2^n value greater than or equal to the number of possible states. So in this case we have 2^3=8 and 2^4=16, so we are stuck with 4 buttons for 10 states, even though 6 of those states are not required. There is no combination of NOT/NOR gates that would allow us to reduce the number of buttons to 2 as we still need 10 combinations for the BCD input.

[0923rio]

@DerekMolloyDCU Is it a 4 pins push button switch you are using or 6 pins?

[DerekMolloyDCU]

@0923rio They are 4 pin momentary push buttons, but the pins are connected in pairs. The connection is made between all 4 pins when the button is held in, but when the button is released one pair of legs is isolated from the other pair of legs. In this video when the button is pressed the two pins on the left are connected to the two pins on the right.

[0923rio]

@DerekMolloyDCU tnx 4 d reply... have you tried using 6 pins? and f u do....can u pls. share to me the pin configurations? f you'd like.... :)

[0923rio]

@DerekMolloyDCU hello sir...tnx for the replies......