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Dynamo output power

jim_easterbrook
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Joined: September 12th, 2016, 3:57 pm

June 20th, 2018, 3:59 pm #1

In another thread the topic of dynamo power output was mentioned. I was in the mood for an experiment this afternoon, so I attached my Microcosm FD4 dynamo (small DC motor in a nicely made bracket) to an electric drill and measured the voltage and current delivered with a range of resistive loads.

The first chart shows output voltage against drill speed for the five different loads. Note that the speeds are approximate - my drill says 3000 rpm on the label, and I assumed the no load voltage to be proportional to speed. (Hence the orange line is dead straight.)
dynamo_VvsO.png
The second chart shows current vs voltage for each drill speed. (To get the power in Watts, multiply current by voltage.)
dynamo_IvsV.png
There's no surprises here really, but it's nice to see some straight line graphs from an actual experiment. Now I just need to work out the optimum speed to drive the bunch of LEDs I'm planning to use and then buy a pulley of appropriate diameter.
Jim Easterbrook, Epsom, UK
http://www.jim-easterbrook.me.uk/

"Science owes more to the steam engine than the steam engine owes to science."
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Dr. Rog
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Joined: December 30th, 2008, 5:53 pm

June 20th, 2018, 4:12 pm #2

Cool work Jim,
Are you intending to use resistors? I didn't on my Wilesco showman's and they work fine
Cheers Rog https://www.youtube.com/user/DrRogB/videos New positive, and successful motto for 2017: carpe diem
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jim_easterbrook
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Joined: September 12th, 2016, 3:57 pm

June 20th, 2018, 4:18 pm #3

I haven't done the arithmetic yet, but I'd like some resistance for protection against unexpected high speed (e.g. broken drive belt to other things being driven). I'm thinking 3 LEDs in series plus a resistor to take the working voltage up to 12, safe voltage up to 15. Or thereabouts.
Jim Easterbrook, Epsom, UK
http://www.jim-easterbrook.me.uk/

"Science owes more to the steam engine than the steam engine owes to science."
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Mehltheuersteam
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Joined: January 24th, 2017, 12:05 am

June 20th, 2018, 6:34 pm #4

Very good experiment... But to be sure, would it do with the real thing, not a drill...
 
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Perry02
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Perry02
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Joined: May 12th, 2018, 11:12 pm

June 20th, 2018, 7:32 pm #5

jim_easterbrook wrote: In another thread the topic of dynamo power output was mentioned. I was in the mood for an experiment this afternoon, so I attached my Microcosm FD4 dynamo (small DC motor in a nicely made bracket) to an electric drill and measured the voltage and current delivered with a range of resistive loads.

The first chart shows output voltage against drill speed for the five different loads. Note that the speeds are approximate - my drill says 3000 rpm on the label, and I assumed the no load voltage to be proportional to speed. (Hence the orange line is dead straight.)
dynamo_VvsO.png
The second chart shows current vs voltage for each drill speed. (To get the power in Watts, multiply current by voltage.)
dynamo_IvsV.png
There's no surprises here really, but it's nice to see some straight line graphs from an actual experiment. Now I just need to work out the optimum speed to drive the bunch of LEDs I'm planning to use and then buy a pulley of appropriate diameter.
Very interesting, I must get educated little byt about this electricity measurements.
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Dr. Rog
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Joined: December 30th, 2008, 5:53 pm

June 21st, 2018, 12:59 pm #6

3000rpm is pretty fast Jim. Is it easy on the engine in question?
Cheers Rog https://www.youtube.com/user/DrRogB/videos New positive, and successful motto for 2017: carpe diem
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jim_easterbrook
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Joined: September 12th, 2016, 3:57 pm

June 21st, 2018, 3:09 pm #7

I reckon I was in that region on this little test I did a while back. I'd like to run the engine slower in the workshop diorama I really am going to build one day. LED lights will reduce the dynamo load, more workshop tools will increase the other load.

(This is a Flickr video, you need to click on the image to view it on Flickr.)
Jim Easterbrook, Epsom, UK
http://www.jim-easterbrook.me.uk/

"Science owes more to the steam engine than the steam engine owes to science."
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Cbwho
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Cbwho
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Joined: February 9th, 2018, 8:53 pm

June 22nd, 2018, 11:32 am #8

What you'll find is that your engine will produce the same watts under full steam no matter what but the pulley sizes will dictate the voltage vs amperage.

I am very curious what the actual power output is in Watts.

My best toy Stirling engine can produce almost a Watt. If you can drive LEDs without a resistor then the Watt output is low.

I found the best load to have to determine this is to drive another electric motor and use two multimeters at the same time (one for volts another for amps).

This generator I believe is one if the better ones for producing more power.

https://www.ebay.com/itm/3-Phase-AC-Mic ... 2526120811
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MrDuck
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Joined: March 5th, 2010, 5:48 am

June 22nd, 2018, 6:30 pm #9

You certainly are more patient than most, Jim.

Very interesting for us working with these micro currents.
Good job!
Et in Arcadia Ego
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Maxwell
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Maxwell
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Joined: June 2nd, 2012, 2:37 pm

June 22nd, 2018, 11:38 pm #10

Very interesting experiment, thanks for sharing the results.
Gone Fishing
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