Mongrel Shark
- Jun 6, 2012
- 260
- Joined
- Jun 6, 2012
- Messages
- 260
So I have stepped up from Joule thieves to Wireless transmission.
Circuit with NPN transistor: Bifilar pancake, one end to base (via resistor if running from much more than 2v) one end to collector. Pos to centre tap, emitter to neg. Thats it. Super simple. If you need to see a drawing, Just like a joule thief with no appliance/load. Do it with speaker wire 2n2222 and flat AAA and it will run down to .3v (or less, I keep disconnecting them, never run one into the ground) and give about an inch of range...
That was a bit boring, so I took 30 meters of cat 5 and a 3055..... 10 cheap Chinese 3055's later and i'm pretty sure the +200v on collector and -300v on base is killing them... Ok that was a bit obvious. Get a good protection diode, and keep amp draw below 500ma, and they last for a while though. I get about 50cm of range at around 3-5 watts. I'm pertty sure I can improve this. I need a switching device that can handle the volts though. Amps is not such an issue. Unless I can double the range, there will be no great need to draw more than half an amp. Higher freq would be good though. I currently have 11-25khz, depending on transistor variation (did I mention they are cheap knock offs?). If I can get a mhz or more I would be very happy.
Which leads me to MOSFET's, Not because I think its the best part, just because I have 2... I have this one, which we will call 4.5v due to gate threshold and this one Which tests with gate threshold of 3.15 On a single heatsink from a plasma I stripped.
I've done my best to google info. watched and read some tutorials etc... Looks like the main problem I will be facing is the negative pulse at the gate. Can I use a protection, reverse bias diode? Like with a regular NPN? Both transistors have gate-source BDV of +/- 30v So I figure the .200-300 I'm getting will kill them in short order. I'm also wondering about gate resistor. I know its not normal practice, but I can see pos up to 30-40v on the base before it goes negitive. with my 3055, this would be pushing the limit for the MOSFET's.. I can upload scope shots if anyone wants to see.
I was also wondering if I can use the two in parallel, and if it would be of benefit. While they both have drain tabs that would normally contact the heatsink, they have been stuck on with insulating thermal tape. So no common drain. They appear to have different roles on the circuit board too. which seems to be some kind of HV driver.
In testing them (with my atlas dca55 semi tester) I also noticed that if you just connect to drain and source, they both test as a diode, with the source being anode, drain cathode and frv of .52v. Is that normal, or are they damaged?
Circuit with NPN transistor: Bifilar pancake, one end to base (via resistor if running from much more than 2v) one end to collector. Pos to centre tap, emitter to neg. Thats it. Super simple. If you need to see a drawing, Just like a joule thief with no appliance/load. Do it with speaker wire 2n2222 and flat AAA and it will run down to .3v (or less, I keep disconnecting them, never run one into the ground) and give about an inch of range...
That was a bit boring, so I took 30 meters of cat 5 and a 3055..... 10 cheap Chinese 3055's later and i'm pretty sure the +200v on collector and -300v on base is killing them... Ok that was a bit obvious. Get a good protection diode, and keep amp draw below 500ma, and they last for a while though. I get about 50cm of range at around 3-5 watts. I'm pertty sure I can improve this. I need a switching device that can handle the volts though. Amps is not such an issue. Unless I can double the range, there will be no great need to draw more than half an amp. Higher freq would be good though. I currently have 11-25khz, depending on transistor variation (did I mention they are cheap knock offs?). If I can get a mhz or more I would be very happy.
Which leads me to MOSFET's, Not because I think its the best part, just because I have 2... I have this one, which we will call 4.5v due to gate threshold and this one Which tests with gate threshold of 3.15 On a single heatsink from a plasma I stripped.
I've done my best to google info. watched and read some tutorials etc... Looks like the main problem I will be facing is the negative pulse at the gate. Can I use a protection, reverse bias diode? Like with a regular NPN? Both transistors have gate-source BDV of +/- 30v So I figure the .200-300 I'm getting will kill them in short order. I'm also wondering about gate resistor. I know its not normal practice, but I can see pos up to 30-40v on the base before it goes negitive. with my 3055, this would be pushing the limit for the MOSFET's.. I can upload scope shots if anyone wants to see.
I was also wondering if I can use the two in parallel, and if it would be of benefit. While they both have drain tabs that would normally contact the heatsink, they have been stuck on with insulating thermal tape. So no common drain. They appear to have different roles on the circuit board too. which seems to be some kind of HV driver.
In testing them (with my atlas dca55 semi tester) I also noticed that if you just connect to drain and source, they both test as a diode, with the source being anode, drain cathode and frv of .52v. Is that normal, or are they damaged?