Input pins and output pin of the error opamp, that's where I would start. You can tell a lot from that.
Jan
Jan
rectified DC in 23.2
V in- 6.78
V in+ 7.08
V out 21.3
I'm using the 6.9 ref so the inputs should be working as intended right? Which would imply the pass transistor or the 556 is acting up?
V in- 6.78
V in+ 7.08
V out 21.3
I'm using the 6.9 ref so the inputs should be working as intended right? Which would imply the pass transistor or the 556 is acting up?
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So the output of the opamp is high, the feedback to the -in is low, and the opamp tries to increase the output as it should.
My guess: incorrect resistor divider from output to -in pin. For 17V out, the resistor ratio should be (17-6.9) to 6.9.
What are those resistor values?
Jan
My guess: incorrect resistor divider from output to -in pin. For 17V out, the resistor ratio should be (17-6.9) to 6.9.
What are those resistor values?
Jan
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oh I got it wrong, slow learner
R6 1.2k
R7 1k
R16 100
I just picked a value between what would give 15 and 18V based on the table from what I had on hand- wasn't terribly concerned with the exact value
R6 1.2k
R7 1k
R16 100
I just picked a value between what would give 15 and 18V based on the table from what I had on hand- wasn't terribly concerned with the exact value
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Comes out to 16V with 1.2k which is fine for my needs, just double-checked those values on the board too.
It still doesn't work, sorry if I gave the wrong impression.
Only other thing I can think of is I'm using a 6.8 Zener to set the voltage, I read through the thread and it seemed good enough for 16/17V. Are there any issues there?
Only other thing I can think of is I'm using a 6.8 Zener to set the voltage, I read through the thread and it seemed good enough for 16/17V. Are there any issues there?
Still the same measurements as before, I just provided the pic to verify the feedback values and/or sanity check- the 16V was just me doing the math.
Took some additional points on the AD817:
+Vs is 22.15
-Vs is 0
Noticed that shorting +in and -Vs with the probe (accidentally) makes the LED light up, not sure what that's about
Took some additional points on the AD817:
+Vs is 22.15
-Vs is 0
Noticed that shorting +in and -Vs with the probe (accidentally) makes the LED light up, not sure what that's about
What's the voltage across R1? And across D5?
I guess the sense points are connected to the force points?
Jan
I guess the sense points are connected to the force points?
Jan
Nothing appreciable across R1 (~1mV) , 7.09V across D5
Also shorting D5 makes makes the LED light up too, at least I know that the D1 isn't broken..
Also shorting D5 makes makes the LED light up too, at least I know that the D1 isn't broken..
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Then there is something wrong with the current source, and/or LED D1. R1 should have about Vled-Vbe. Is Q2 the right polarity?
The cs should be fixed first.
Jan
The cs should be fixed first.
Jan
Q2 is BC556BTA, I replaced it and same behavior, although I get 0.5V across R1 now. LED still turns on then off
Can you check that the zener in series with the opamp output is the correct value and the right way around?
Jan
Jan
I think that did it, I swapped the diode direction and it seems to work perfectly, LED on and 16.3V!
Thanks so much for the extensive support! Looking forward to building another one!
Thanks so much for the extensive support! Looking forward to building another one!
Hello
...perhaps it's a boring question and has been answered already but could someone explain step by step what changes have to be done for a 5v output operation..
I would really appreciate the simple and straightforward explanation 🙂
many thanx
K.
...perhaps it's a boring question and has been answered already but could someone explain step by step what changes have to be done for a 5v output operation..
I would really appreciate the simple and straightforward explanation 🙂
many thanx
K.