Hello;
I'm building a light-gate - 8 irleds pulsed at 38khz. A nano or digispark can take care of that. Can someone take a look at this pcb/circuit? It's <2" so panelizes cheaply, and I'll make the pads freaking huge for easy soldering.
Transistor - 2n2222a
Res1 - 2.2k goes to arduino pin
Res 2 through 9 - 330?
TSAL6200s - Frwd V is 1.35v each.
Power in = 5v battery pack.
Do I need anything else? Capacitors for some reason? I've seen some posts talking about shunt-resistors?
Res 2 through 9 - 330
Well that will only put 11mA through each diode. Given that the data sheet says the absolute maximum is 100mA continuous ans 200mA peak, you are under running them greatly. Is the reason for so many diodes to get brightness? If so you could well get more from each individual LED.
I've seen some posts talking about shunt-resistors?
Name names, or rather post links, I can't see any reason for a shunt resistor.
Capacitors for some reason?
The reason would be power supply decoupling, you could use a 47uF if you pushed up the LED current.
Can someone take a look at this pcb/circuit?
Without the accompanying schematic it is a waste of time. How was it created? Did you use a net list from schematic capture? I would make the tracks thicker however.
The 8 TSOPs are going 5' across to 8 separate receivers (TSSP58038), at 8 different heights (into a NOR gate). I figured I can lower the resistors safely and bump the led's output. Not sure how much I really want/need.
Okay, if I only need caps for decoupling, and no concern at this power level, I'd happily keep the circuit simple.
Redirect Notice talks about a shunt-resistor, and shows a much improved waveform. But I basically see no other similar examples in any other ir circuits I've found.
I'll definitely increase the track thickness, thanks.
No accompanying schematic, I'm doing it from scratch and avoiding breadboarding. I'll try generate one.
Thanks for the link. That circuit he uses does not seem to make sense. There is only a 1R series resistor limiting the current which means that if the supply were up to it then the LED would take 3.65A which is some what alarming for an LED with an absolute maximum of 100mA.
His power supply is not capable of that and the current is being limited by its impedance. I think I can see what is happening, the slow waveform is actually caused by the 22uF decoupling capacitor being fully discharged with the LED on. I think he is fooling himself by thinking one waveform is an indication of better performance than the other. I think his grasp of electronics and reading data sheets is suspect at best.
I'll try this again. Huge pads, big traces. 8 TSAL6200s from 1 2n2222a. I think I can use the schematic on the left side of the image (although I'm not running it as a 2/series, but a true parallel). I think the schematic matches up with the very simple PCB, which basically just has a ground (bat -?) plane and +5v plane.
Edit: My 2.2k was reversed for some reason. Flipping it cleans up that trace.
Yes that looks fine once you flip round that 2K2.
