The 78L05 ground pin shouldn't actually be attached directly to ground; it should be attached to ground via the 1N914 diode. It's a trick Madbean uses to boost the performance of the PT2399 by running it a little above 5v, which is barely in spec. You'll have to scooch the link between 5-K and 5-O over to column 8, perhaps, and then cut the trace at 5-O. Something like that. Or just remove the 1N914 and run the PT2399 at 5v.
I built this and it works well. Having the internal trimmer for feedback is a really nice feature ... you can get a lot more useful range out of the feedback pot.
Still, I'm having a helluva time with my DIY LED/LDR combo for the bloom feature, and that's really the claim to fame of this device. The LED just isn't getting bright enough to interact with the LDR. I ended up replacing the 100K resistor with a 100K trim pot and even at zero it's just not enough. I'm going to mess around with different LED's or maybe add more gain to the LM386 by adding a cap across pins 1 and 8. It will eventually work. I should have sprung for an actual NSL32R vactrol but I was too cheap.
The LDRs out there with the widest swing that I can find are NSL-19M51. They are about $0.90 each and have 5k/20m light/dark resistance. That and a superbright white LED might do the trick.
The 78L05 ground pin shouldn't actually be attached directly to ground; it should be attached to ground via the 1N914 diode. It's a trick Madbean uses to boost the performance of the PT2399 by running it a little above 5v, which is barely in spec. You'll have to scooch the link between 5-K and 5-O over to column 8, perhaps, and then cut the trace at 5-O. Something like that. Or just remove the 1N914 and run the PT2399 at 5v.
ReplyDeleteHmmm, no, column 8 isn't free. Maybe a double-link at 6-O and use column 6? You're way better at this than I am.
DeleteThanks for noticing this, Michael.
DeleteThe layout is updated.
I built this and it works well. Having the internal trimmer for feedback is a really nice feature ... you can get a lot more useful range out of the feedback pot.
ReplyDeleteStill, I'm having a helluva time with my DIY LED/LDR combo for the bloom feature, and that's really the claim to fame of this device. The LED just isn't getting bright enough to interact with the LDR. I ended up replacing the 100K resistor with a 100K trim pot and even at zero it's just not enough. I'm going to mess around with different LED's or maybe add more gain to the LM386 by adding a cap across pins 1 and 8. It will eventually work. I should have sprung for an actual NSL32R vactrol but I was too cheap.
The LDRs out there with the widest swing that I can find are NSL-19M51. They are about $0.90 each and have 5k/20m light/dark resistance. That and a superbright white LED might do the trick.
Delete