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0-30V Stabilized Power Supply

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audioguru

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Re: 0-30V Stabilized Power Supply
« Reply #1498 on: April 13, 2013, 02:17:29 PM »
Hi, is there any place in the circuit of this project, where safely, without any harmful consequencies or bad interference to other parts of the circuit, could be added additional LED diode, which should be on all the time, when the power supply is on?
The rectified and filtered +40V can light an LED if it has a current-limiting resistor.
An LED is 1.8V to 3.8V depending on its colour. If the LED is a 1.8V red one then for 15mA the resistor is (40V - 1.8V)/15mA= 2547 ohms. Use 2.7k. Its power is a little more than 1/2W so use a 1W or 2W resistor.

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Re: 0-30V Stabilized Power Supply
« Reply #1499 on: April 13, 2013, 02:35:50 PM »
Did you mean exactly this place is the best to connect an LED? (modification in red color).

audioguru

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Re: 0-30V Stabilized Power Supply
« Reply #1500 on: April 13, 2013, 04:22:40 PM »
Did you mean exactly this place is the best to connect an LED? (modification in red color).
Yes.

sobol

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Re: 0-30V Stabilized Power Supply
« Reply #1501 on: April 14, 2013, 04:37:12 AM »
Does someone have any ideas what's wrong with my circuit?
Since your U3 opamp does not perform correctly as a comparator then replace it.
I replaced it with 3 other opamps, and the effect is still the same.

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Re: 0-30V Stabilized Power Supply
« Reply #1502 on: April 14, 2013, 09:07:25 AM »
Thank you, but I have a few other questions:
1)Is there any way to disable that voltage load on filtering capacitor, because after turning off, there is still voltage in the output, which gradually dissapears.
2)I want to add an additional switch for 'fast toggle ON/OFF of the output', so I should not need to turn off the power of all supply. I think the best place is the output + (see attached image), but then it could be a problem to a switch, when current and voltage are set to MAX and there is heavy load on the output. During turning on/off the swich can be damaged by the high current sparks inside it's inner contacts? So, maybe there is other good place, where the current is small, but inserting there a swich, could trigger the output ON or OFF? Thank you.

audioguru

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Re: 0-30V Stabilized Power Supply
« Reply #1503 on: April 14, 2013, 09:43:09 PM »
Why do you add a switch to force the output to the positive unregulated voltage?
Don't you want a switch to force the output to 0V?
Then add a switch to the input of U2 and ground.

sobol

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Re: 0-30V Stabilized Power Supply
« Reply #1504 on: April 15, 2013, 03:30:27 AM »
I have fixed my ps, P1 was wrongly soldered. I have believed that pin order in pcb is correct... it's not.

Why do you add a switch to force the output to the positive unregulated voltage?
Don't you want a switch to force the output to 0V?
Then add a switch to the input of U2 and ground.

Inverting or non-inverting input?

audioguru

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Re: 0-30V Stabilized Power Supply
« Reply #1505 on: April 15, 2013, 06:09:15 AM »
Inverting or non-inverting input?
U2 is a non-inverting amplifier. Pin 3 is its input and pin 2 is used for negative feedback.
If you ground pin 3 then the output transistors will turn off and the load will discharge the output capacitor.
If the load current is low and the output voltage is high then it might take a long time for the output voltage to come down.

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Re: 0-30V Stabilized Power Supply
« Reply #1506 on: April 15, 2013, 08:59:33 AM »
Quote
Why do you add a switch to force the output to the positive unregulated voltage?
Don't you want a switch to force the output to 0V?
I don't understand, what do you mean here? I think, there is no difference where to connect a switch, on + wire or - wire...
Why is it bad to connect a switch like I said?

KevinIV

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Re: 0-30V Stabilized Power Supply
« Reply #1507 on: April 18, 2013, 08:32:38 PM »
Question it doesn't look like a bad place to put a power on/off LED. It should turn off rapidly.

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Re: 0-30V Stabilized Power Supply
« Reply #1508 on: April 20, 2013, 12:51:48 PM »
Hi, C7 capacitor should be changed to film capacitor with a resistor in parallel. What would be the best values for them?
Use 10uF for a film capacitor for C7 with a 4.7k/0.5W resistor in parallel.
This does not help, current limit LED still turns ON on minimum P2 potentiometer value, even with no load on the output...  :(

sobol

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Re: 0-30V Stabilized Power Supply
« Reply #1509 on: April 21, 2013, 07:39:38 AM »
Can I increase output voltage with voltage calibration trimpot without any consequences? Or it's not recommended?

audioguru

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Re: 0-30V Stabilized Power Supply
« Reply #1510 on: April 22, 2013, 10:41:58 PM »
Can I increase output voltage with voltage calibration trimpot without any consequences? Or it's not recommended?
Then at maximum output current you might have ripple instead of voltage regulation.
That was a problem with the original circuit that used a 24VAC transformer.

nitro199

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Re: 0-30V Stabilized Power Supply
« Reply #1511 on: April 23, 2013, 01:37:14 AM »
Hi, i`m gattering all information that i can get :D i read entire topic and found 3 or 5A versions, but maybe there is any chance to get 7 or 10A with thease shematics?