anyone tried this? I'm curious as to how well it'd work, I'm trying to get plans together for an install that will have a fair amount of decorative lighting, and I'm pretty sure that I can get enough light to the transistors to make them turn on....

[ February 20, 2004, 04:54 PM: Message edited by: Sassmaster ]

 

Yeah it will work if you get enough light to them but I don't really understand why you would want to do this? It doesn't have any functional advantage and you still have to run a 12V source to the transistor. Are you just doing it for the sake of doing it?


Here would be the schematic if you need it

+12V
| Emitter
/
Base | V
Light-> _|/ PNP Transitor make sure it
|\ can handle about half and amp
| \ to be on the safe side
|
|
| Collector
To Rem. on Amp

 

ACK.. it butchered my schematic! If you need the schematic let me know and I'll email it to you.

 

actually, we just ran through a lab on this in trade school, so I have the schematics here that I need, I just want to do it because it'd be different, and it'd save having to run a wire where I didn't have to.

I like trying new things, just to see if they can be done, and to see if they are practical.

 

You would still need to run a power and ground wire (curent loop) to the photo-transistor to turn on a relay or high current transistor. If the light source was removed, even momentarly the circuit would shut off, you would need some delay to compensate for this.

Can it be done, yes.
Is it practical, no.

If you want to be creative try using a little class III laser diode (cheap from digikey or electrosonic) to turn on the photo-transistor, you would only need about 1mA, and the effect would be neat if you had some smoke and mirrors.
Good luck J

 

I was thinking of opening up the amp, soldering the phototransistor across the remote and power terminals, and drill a small hole in the casing (big enough to let in the light) and do it that way.

 

Hey
you would have to have lots of light to have enough current flow to turn the amp on if you are sticking it in the amp itself.
What type of amp is this going in? If it's a relay input you need more than the phototx, if it is an active input you could get away with just the phototx.
You still need some amount of capacitance to ensure the amp won't shut off if the light momentarily disappears or changes position when going over a bump.
J

 

Spoke to my electronics instructor today about it, got some concrete pointers, so I'm gonna try a mock up tomorrow in electronics, I'll post how well this works. going to be the photo transistor, with a small cap, then a 10K resistor, to a switching transistor direct to the remote, here's hoping it works! LOL

 

Worked on it today, and I got it to work on a little pyramid amp that I had in the garage holding down some sawdust. next step is to try it on something else. probly my MTX amps first, then the ones that'll be in the actual install

 

Working flawlessly, using a cold cathode tube, even through a pinhole, on a relay activated amp, it will turn on from 3-4 inches away.