You mentioned in an earlier post that the RS 25 ohm pot goes down to 0.3 ohms. that low reading is probably the test prod leads. Touch the test prods together and you will likely read between 0.3 and 0.5 ohms.
I point this out here because now that a bunch of you are working with low impedance circuits, you need to account for stray readings.
yeah that's a good point mike! you will get losses somewhere in the circuit because everything isn't 100% efficient, even the capacitor can lose a couple of millivolts for you! the pot might loose abit of power, and the LM317 uses the power to regulate. so you have to take that into account as mike said.
good luck guys!
Well I am using a cheap meter, but it does register the same as a decent RS one I bought years ago. And it does zero out with the probes touched together.
Xenodius has the same rheostats and when measured with his dad's Fluke meter, he gets the same readings. The Fluke is a much better meter than any meters I have.
i just got my parts today
Yay!
I'm gonna build it tonight hopefully.
So, with the resistor you used, Daedal, the 4 0hm, what current do you get out, no pot?
Thanks
Jonno
Daedal, Great job on the circuit explanation - however, you say the 1N4001 diode reduces the voltage to the LD but it's in reverse polarity (so is in fact an open in normal operation).
Thank you Zax. Although, it's not an open circuit. It would be an open circuit if the diode was connected in the right polarity. That's why it works for reverse polarity protection.
For the 1N400X diodes to drop the voltage, you'd need to put them in series with the LD. That's something I had meant to fix in the guide several times before and kept forgetting. Thank you for reminding me.