Stepper Motor Generator - Various Rectifier Circuits - 1

This is a compilation video. The object was to try 4 different rectifier circuits to see which yielded the most power at maximum sustained running speed of a Jensen 25 engine.
In the end I don't know if the circuit that worked the best in fact IS the best in terms of potential voltage and current. All I know is what made the meter go the highest.

This is part 1, since the video was too big to fit within youtube limits (never thought THAT would happen)

Category:

Howto & Style

Tags:

• Bridge
• Rectifier
• Circuit
• Electronics
• Stepper
• Motor
• Steam
• Engine
• Jensen
• 25

[xexorz]

What load were your alternators under, or we're they just free-wheeling?

Volts * Amps = Watts (POWER)

Voltage all by itself isn't much good to you.

Also, try to use low Vd (voltage drop) diodes. Faster diodes are generally better too. Try Shottky diodes

[MisterOcclusion]

I don't think there was a load on these (been a long time). Those particular motors were so tight that this engine was having enough difficulty with them on their own.

I do recall looking for the diodes you mention (our electronics stores aren't terribly well stocked), but I was unaware that the shottky diode could be used as a rectifier.

[spencermcgrew]

I recently began experimenting with a Jensen model 25. I constructed an extremely crude dynamometer out of a lego motor and gear train that I connect a multimeter to. In the end at maximum pressure I measured 14 volts and .25 amps. This translates into 3.5 watts. This was only for short bursts and my rig was less than friction free but it provided an important lesson--the utter inefficiency of the reciprocating steam engine.

I also realized that the boiler horsepower was insufficient.

[MisterOcclusion]

High cost for little return isn't good, but if you're having fun doing it, then it's a hobby and no different from many others in that regard. ;)

They do run at too low a pressure to realize their potential. I know a bloke who had a Jensen 20 running at 60psi and he was cranking out some impressive power.

Uprating the SV on my own 20 to blow off at 30 instead of around 19 made a noticeable difference. It won't hold 30 for long, but will hold at 25.

[Nolte919]

If you connect two rectifiers between the ends of the coils you should get double the voltage but half the current as connecting four rectifiers between the ends and center taps. In either case you should get the same power because "power = volts x current". So if with two rectifiers you have 12 volts and .5 amps you'll have 6 watts of power. Similarly, if with four rectifiers you get 6 volts and 1 amp you'll also get 6 watts of power.

[MisterOcclusion]

In theory it should work like that. In the time since posting this we've found that there really isn't much advantage to using the bridge rectifiers unless you really want more voltage. They don't see an advantage over a simple diode circuit until up near 28 volts or so where the latter falls off. The cost of using more diodes (for the bridges) is that each one takes a measure of your current. For these low voltage generators the efficiency becomes less than good because of this.

[aseglkj]

normal diodes are too inefficient. you lose 2V per bridge rectifier. you should use schottky diodes like the 1N5820.

[cgod241]

I missed haow many watts did you draw"???

[DhrTressie]

Stepper motors make just about the worst, most inefficient electrical generators available. Ever noticed how difficult they are to turn, even with no electrical load connected? That's energy lost, even before you've done any useful work.

[zarboar]

That is so cool.

[VideyoJunkei]

less diodes= less loss(.6v a diode!), so fewer rectifiers should provide more output.

Maybe you could only use 2 diodes using the full winding? (assuming the wiring phase is right)

[TheMrBlinx]

I chucked a stepper into a drill - at highest speed, it put out an astounding 220+ volts AC. Step that down with a transformer, voltage goes down but current goes up.

[MrNigel1340]

Thank you, a very interesting video, its amazing what these small stepper motors will put out, do you know of a site on the web that shows wiring diagrams on how to rectify stepper motor output please, regards Nigel aka Doc Cox

[beehard44]

some stepper motors. you can get 6+volts from only 200rpm...

[harryman11]

why use a stepper motor instead or a regular generator set up is there an advantage, higher voltage?