View Single Post
 
Old 02-14-2011, 06:00 AM
chuck H's Avatar
chuck H chuck H is offline
Senior Member
 
Join Date: Nov 2010
Posts: 168
Phototransistor

Quote:
Originally Posted by Lidmotor View Post
Chuck---- I'm glad that you got that to work. I worked with this idea all week and found that if you wrap plain old aluminum foil around the cartridge you get almost a volt with enough punch to run the circuit. I used just plain tap water with no additive. The foil seem to hold up amazingly well. You can't beat the cost and availability.
I decided to use an infrared phototransistor between the base and emitter of the 2N2222 to solve the on/off problem instead of using John's way. It is an easy idea but not my idea. I saw it done somewhere before and it works very well except that when it shuts down the circuit it still leaks about 100 to 200 micro amps. For the battery situation we have-- where all we care about is turning the light on and off ---it works just fine. The Radio Shack part# is 276-0145 and here is a link to the part:

Infrared Phototransistor - RadioShack.com

The thing looks like a white LED. The collector (short end) goes to the base of the 2N2222 and the emitter (long end) goes to the 2N2222 emitter. When light hits it the device keeps the transistor from functioning. Sensitivity is controlled by adjusting the base resistance.

@Mikrovolt
I enjoyed your link to the article on magnesium. That really helped.

Cheers,

Lidmotor
@ Lidmotor,
Thanks for the info. I am making some of these for around the house in vases and planters and the photo cell will work great for the small applications. I have been working with the aluminum but have not found the combination I'm happy with as of yet . I have many things going on with this stuff and sometimes need to walk away from a couple to finish others.... Thanks everybody for all the info.
__________________
 
Reply With Quote