Last night a breadboarded this pretty basic circuit. I've got a 12v wall wart running into an LM7809 voltage regulator with a transistor bypass. This part all seems to work just right. My goal is actually to get around 6 volts (to run a speaker) and 5 volts (to run an MP3 player).
So from the 9volt output of the regulator & transistor, I ran it into 4 1N4001 daisy chained and that gave me about 6.3 volts (according to my multimeter) and then chained 2 more off of it to get my roughly 5 volts (again, from the multimeter.) At the end, I ran a 1M resistor to ground. So I was getting about 0.7 volt drop per diode.
Last night I breadboarded it, everything worked beautifully. I left it running for a couple of hours, no problems at all.
So today I soldered it all together and the output from the voltage regulator is 9v, but the diodes aren't dropping nearly as much as they were last night. Now I'm getting about 0.3 volt drop per diode.
I don't have a lot of diodes to choose from. I have the 1N4001s, 1N4739s, 1N4148, 1N5817, and 1N914s. The 1N4001s seemed like they'd be the best choice, but maybe not.
How could the voltage drop have changed so much, though (there's no detectable heat to the touch from them).
Thanks for any enlightenment anyone can provide.
So from the 9volt output of the regulator & transistor, I ran it into 4 1N4001 daisy chained and that gave me about 6.3 volts (according to my multimeter) and then chained 2 more off of it to get my roughly 5 volts (again, from the multimeter.) At the end, I ran a 1M resistor to ground. So I was getting about 0.7 volt drop per diode.
Last night I breadboarded it, everything worked beautifully. I left it running for a couple of hours, no problems at all.
So today I soldered it all together and the output from the voltage regulator is 9v, but the diodes aren't dropping nearly as much as they were last night. Now I'm getting about 0.3 volt drop per diode.
I don't have a lot of diodes to choose from. I have the 1N4001s, 1N4739s, 1N4148, 1N5817, and 1N914s. The 1N4001s seemed like they'd be the best choice, but maybe not.
How could the voltage drop have changed so much, though (there's no detectable heat to the touch from them).
Thanks for any enlightenment anyone can provide.