generators

[Trevor]

Hee Hee Hee Thanh - and I thought I was funny. I didn't realize that the light was from your genny on your model. Nice Job and I guess your going to dress it all up just for me.
On another note - I have finished painting the model up and yep! you guessed it Ian, You put the gremlins onto me and the model wouldn't run first up. I forgot to put in the new bearing and now it goes pretty well. Photo up tomorrow night.
Trev

[Trevor]

Hi Hanhn - here is the last picture of the diaphragm Engine, now painted and working well.
Trev

[derwood]

Video?

[Ian S C]

Don't put it in the wheelie bin, if your's is the same as ours that's the recycle one. Looking very good, well done that man.
Ian S C

[Trevor]

Thanks Ian, I wheely wont LOL.
Sorry Derwood no video until I get myself organized with Utube.
Trev

[thanh-cuibap]

Hi Trevor !can you set up one generator ???

[Trevor]

Yes Thanh - It originally had a generator on it, but with the load of the fan and the pump the engine wanted to go slow and I didn't want to use a bigger flame. Hence the fan only and it runs very well on a small flame.
Trev

[Binder]

Don't think anyone mentioned automotive generators. Is it not a splendid idea to use generators from scraped cars?

Btw can someone say the relationship between generator - size of Stirling - heat required.

PS. I'm looking for existing solutions. Don't have capacity/knowledge to experiment.

[Ian S C]

The alternator of a modern car takes about 3hp to generate not a lot, a generator from an older car is actually a better proposition, it's self exciting (doesn't need a battery), it produces DC current without needing a rectifier.
Here's my little alternator set up with a 3hp motor.
Ian S C
[img]

DSC00844 (640x480).jpg (223.18 KiB) Viewed 13709 times

[/img]

[cbstirling2]

How do I measure the current output of a small dc generator (toy motor), do I just use 1000 ohm resistor in series with the mulitmeter as the load to measure the current?

How does the 1000 ohm resistor affect the reading?

[Trevor]

High CB - Most multimeters will have current reading on them. You should be able to measure from 50mA, 250mA and even up to 10Amps.
The 10Amp range on a meter is quite good. The red lead from the multimeter will go to the generator positive side and the black lead from the meter will go to the either what you are driving or straight to the generator negative. This will give you the max amp reading the generator can do.
Trev

[cbstirling2]

Trev, I tried that and it read infinite... i definitely need a load on the generator. Due to Ohm's law.

From the internet:
"Multimeters have an incredibly high input impedance. If you connect your meter directly to the output of your circuit and ground you will be loading your circuit with this high impedance. If you put a shunt resistor on the output and measure the volt drop across that resistor then by ohms law you can calculate the output current." Ohm's law is V=I*R

When I used a 1000ohm resistor, conveniently the output read 4v and the amp meter inline read 4 milliamps. 4*4/1000=0.0016 Watts

It's a little disappointing how little power this is producing, I wonder what the true power of my little engine??

[Ian S C]

I,v spent many hours trying different loads, pulley sizes, and different generators and alternators. Alternators have the advantage of no brushes, so reduced friction, but if you want a DC current you lose about .5V for each diode in the circuit which is a large % on low voltages.
Ian S C

[Trevor]

If you can get a small 3phase or stepper motor, ie from an old video machine, you are very much there. They spin easily and will produce AC voltage which can be rectified and at low rpm. All the small DC motors I have tried need to be run at a few thousand revs and this makes it hard. Jaycar do have a small 9vDC generator but it also requires at least 3000 revs to do any good, however, it does put out a couple of hundred mA.
Also for measuring amp loads when testing small dc motors, I normally use an analogue meter and not digital. I find due to the high impedance that they read incorrectly.
Trev

[cbstirling2]

According to the specs, the toy alpha spins at 1700 RPM.
The drive pulley is at least twice the diameter of more as the generator. So the generator spins at least 3000 rpm.
I also used an analog meter to double check the amp output and got the same value.
Next time I will try different shunt resistor sizes.
I will try 100k next.
I have surplus stores here but it's a bit hit and miss what I find there.
Is there a particular AC motor that I can get online?