Can you confirm the 0V line at the output is really connected to the center tap of the transformer please.
Brian.
Right, but I guess it's just a drawing error. The problems have been reported with the negative supply.1) The diodes in upper half of the picture would appear to be (so you might expect ca. +1.2V at diodes / 1.2kOhm point), but diodes in lower half of the picture wouldn't be because they are put in non-conducting direction.
This could only happen, if the input voltage is below about 14 V, respectively the resistor current below 1 mA. Should be O.K. in normal operation with a 15V transformer, but one would want to give some extra current to the diodes.somewhere inside that range, diodes wouldn't be conducting & thus not provide ~1.2V across them.
??? The circuit is just O.K. and the suggested method to build a variable resistor. It has the advantage, that the resistance can't go above a maximum value with a faulty wiper. Otherwise, the output voltage would possibly rise to unwanted values.3) Use of the adjustable resistors seems a bit weird: I suspect you'd want LM317/LM337 Adj pin connected to wiper, not to (wiper and one side of adjustable resistor).
We used standard electrolytic capacitors,You should also observe, that the 10 uF capacitors must tolerate polarity reversal, so tantal capacitors are unsuitable.
I gather you're using sets of 2 series diodes as a ~1.2V reference voltage, to offset LM317/L337 Vref so you can adjust output voltage down to 0V?
Yes it is.Can you confirm the 0V line at the output is really connected to the center tap of the transformer please.
Brian.
It's a drawing error I made the correction in the schematic! And I have label the components too!but diodes in lower half of the picture wouldn't be because they are put in non-conducting direction.
Indeed! By the way: attachment link broken :?: Edit: I see link is fixed, but where it says "15V" you should read "0V" since you're using this as ground. AND: 15V AC != 15V DC. If you don't understand that, look up "alternating current"... concept of AC & how voltages / currents vary in time, is essential in understanding a circuit like this (blue line marked "pulsating" is what you'd expect as voltage across the 1000uF capacitors).We passed 15 minutes studying the circuit and they allow us 5 hours to build it on a protoboard but nobody fully understand it.. that's stupid
5 hours to study it and 15 minutes to mount it would have been better!
I'll bite:Does someone would be able to explain me how the current and voltage are distributing in the schematic ....
AND: 15V AC != 15V DC.
By the way: attachment link broken
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