RCCrawler Forums

Charlie-III · 11-04-2012, 07:00 AM

OK, I have a photo-cell as a tach on my motor dyno. I killed another "flashlight bulb" that's been used as the light source. I was thinking of replacing it ONCE with a white(?) LED as the light source. Will it work?

I don't know anything about the photo-cell other than the dyno was built ~25 years ago.

I want this dyno back up to do some testing.

TIA.

PS, the light source is on the case of the dyno with the photo-cell ~3/4" away with a light guide tube on it, parallel with the shaft. A shaft coupler goes between the "load motor" (basically now a generator) and the test motor. The shaft coupler has 2 aluminum "blades" that interrupt the light and the resulting voltage from the photo-cell drives a RPM display. The photo-cell "may" be from a prop tach used for model airplanes.

heyok · 11-04-2012, 08:18 AM

Probably worth a try.

Maybe you can mount up a white LED inside the base from the old bulb.

Do you have a white LED to try?

What voltage goes to the socket? Need to know that to calculate the resistor value.

Docwolf · 11-04-2012, 11:21 AM

It would be a perfect upgrade.

Charlie-III · 11-04-2012, 01:36 PM

Thanks for the replies guys. I have yet to pull the dyno apart, so I don't know what is in there.

When I do, I will reply here and make a post in "Cordwoods" dyno thread. I really want to do a comparison of my dyno to a few others.

SuperRoo · 11-05-2012, 07:52 PM

I had a little play with a garden light with a photocell in it and tried with a 205 lumens led torch (Flash Light) on high and low and it worked fine.

I tried with a couple of other white leds, some low power fluro lights and even a fibre optic light and had very poor success.

Only the super-bright 18000mcd ≥ leds would turn the light off. The fibre optic didn't even come close, I thought it would on the end but I think the light was too concentrated (small). The led ≤ 18000mcd wouldn't turn the photocell off.
I even tried the 18000mcd on a higher resistant value (with a led tester) and it still turned it off. The 9000mcd led even with a lower resistor value wouldnt turn the garden light off.

Charlie-III · 11-06-2012, 05:39 AM

Thanks for the testing SuperRoo.

11-04-2012, 07:00 AM	#1
Charlie-III I wanna be Dave Join Date: Nov 2010 Location: 07456 N. NJ USofA Posts: 8,314	LED as light source for photo-cell?? OK, I have a photo-cell as a tach on my motor dyno. I killed another "flashlight bulb" that's been used as the light source. I was thinking of replacing it ONCE with a white(?) LED as the light source. Will it work? I don't know anything about the photo-cell other than the dyno was built ~25 years ago. I want this dyno back up to do some testing. TIA. PS, the light source is on the case of the dyno with the photo-cell ~3/4" away with a light guide tube on it, parallel with the shaft. A shaft coupler goes between the "load motor" (basically now a generator) and the test motor. The shaft coupler has 2 aluminum "blades" that interrupt the light and the resulting voltage from the photo-cell drives a RPM display. The photo-cell "may" be from a prop tach used for model airplanes.

11-04-2012, 08:18 AM	#2
heyok I wanna be Dave Join Date: May 2007 Location: Vancouver, BC Posts: 2,379	Re: LED as light source for photo-cell?? Probably worth a try. Maybe you can mount up a white LED inside the base from the old bulb. Do you have a white LED to try? What voltage goes to the socket? Need to know that to calculate the resistor value.

11-04-2012, 01:36 PM	#4
Charlie-III I wanna be Dave Join Date: Nov 2010 Location: 07456 N. NJ USofA Posts: 8,314	Re: LED as light source for photo-cell?? Thanks for the replies guys. I have yet to pull the dyno apart, so I don't know what is in there. When I do, I will reply here and make a post in "Cordwoods" dyno thread. I really want to do a comparison of my dyno to a few others.

11-05-2012, 07:52 PM	#5
SuperRoo Quarry Creeper Join Date: Dec 2008 Location: Australia Posts: 269	Re: LED as light source for photo-cell?? I had a little play with a garden light with a photocell in it and tried with a 205 lumens led torch (Flash Light) on high and low and it worked fine. I tried with a couple of other white leds, some low power fluro lights and even a fibre optic light and had very poor success. Only the super-bright 18000mcd ≥ leds would turn the light off. The fibre optic didn't even come close, I thought it would on the end but I think the light was too concentrated (small). The led ≤ 18000mcd wouldn't turn the photocell off. I even tried the 18000mcd on a higher resistant value (with a led tester) and it still turned it off. The 9000mcd led even with a lower resistor value wouldnt turn the garden light off.

11-06-2012, 05:39 AM	#6
Charlie-III I wanna be Dave Join Date: Nov 2010 Location: 07456 N. NJ USofA Posts: 8,314	Re: LED as light source for photo-cell?? Thanks for the testing SuperRoo.

11-04-2012, 11:21 AM	#3
Docwolf RCC Addict Join Date: Jun 2011 Location: Lindsborg Posts: 1,708	It would be a perfect upgrade.

LED as light source for photo-cell?? - Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Led: Light buckets	BrianP	Electronics	2	01-04-2011 03:08 AM
use LED keychain to light it up~	xxgg	Electronics	0	03-20-2010 09:12 PM

Sponsored Links

RCCrawler Forums

Thread: LED as light source for photo-cell??