Adjustable power supply PCB design problem

[Xlll]

I made a PCB Design for adjustable power supply circuit.
But I face some problems ... My real design doesn't work although it was work on simulation and testboard...but for pcb it doesn't...I checked the connection, soldering and made sure that all component work ...but in pcb I find that one of two diodes made short circuit from both side and I tried to change it but after remove it I found that diode is still working ...making this with two another diodes I think that the problem my by in my design, and the same thing happened with LED, and my instructor didn't find out the problem
Can anyone tell my where is the problem here and if I will face another problem?... I post also picture of my design on PCB and simulation

 

[betwixt]

You won't win any awards for that PCB layout, I advise you to read the data sheet for the LM317 carefully.

You should place C2 and C4 very close to the regulator, track length is critical. Also move C1 closer to the rectifier and use wider tracks to reduce resistance and impedance. Flood filling the ground would help.

Brian.

 

[barry]

1) Just saying "it doesn't work" doesn't tell us anything.
2) You don't even say which diode measured short.
3) You don't tell us about any of the voltages in your circuit that you've measured. Do you even have a DC voltage at the output of your bridge?
4) What "same thing" happened with the LED?

 

[Xlll]

1) Just saying "it doesn't work" doesn't tell us anything.
2) You don't even say which diode measured short.
3) You don't tell us about any of the voltages in your circuit that you've measured. Do you even have a DC voltage at the output of your bridge?
4) What "same thing" happened with the LED?

"It doesn't work " I meant it doesn't give me DC output voltage ... D3 measured short
LED didn't emit light in PCB but when I separate it from circuit it emits light

 

[KlausST]

Hi,

a PCB layout is more than just connecting all the devices according the schematic.
It has big impact on the function of a nowadays circuit.
It has impact on noise, precision, accuracy, but also on frequency response and stability. In worst case the PCB layout is responsible whether a circuit will work reliably or refuse to work.
It has impact on how sensitive the circuit is against HF noise from external sources (cellular phone, WiFi, bluetooth...) and whether your device interferes with other wireless connections.

It also has impact on non electrical measures like heat spreading, mechanical stability, mounting..

Some basic hints for a good PCB design are: using a GND plane and keeping traces as short as possible.

Klaus

--- Updated Jun 24, 2022 ---

I meant it doesn't give me DC output voltage

So what does it do?
* really give 0mV DC?
* does it oscillate?

Please show photos:
* of the soldering side
* and the component side
(100kByte each should be sufficient)

Klaus

 

[stenzer]

Hi,

"It doesn't work " I meant it doesn't give me DC output voltage ... D3 measured short
LED didn't emit light in PCB but when I separate it from circuit it emits light

what's the output voltage of your rectifier? Have you tested D3 also with a diode tester, by menas does it block the the current in one direction and let the current pass it in the other direction. Note, D1 and D2 are in an anti-parallel configuration to D3. How have you determined the short circuit of D3, cathode of D3 with respect to GND?

Have you checked the proper mounting orientation of the rectifier, the LM317 and the diodes?

BR

 

[wwfeldman]

your circuit looks (essentially) identical to one on the LM317 data sheet

what is the input voltage to the LM317?

what position is the pot wiper in?
if you turn the wiper to full clockwise, full counterclockwise, and about halfway,
what do you expect as output, and what did you measure on your circuit?

is the LM317 in correctly? I have put similar parts in backward in the past.

I suggest you add a resistor in series with the pot, so you cannot,
by turning the pot wiper, connect the adjust input to ground

 

[tepalia02]

I made a PCB Design for adjustable power supply circuit.
But I face some problems ... My real design doesn't work although it was work on simulation and testboard...but for pcb it doesn't...I checked the connection, soldering and made sure that all component work ...but in pcb I find that one of two diodes made short circuit from both side and I tried to change it but after remove it I found that diode is still working ...making this with two another diodes I think that the problem my by in my design, and the same thing happened with LED, and my instructor didn't find out the problem
Can anyone tell my where is the problem here and if I will face another problem?... I post also picture of my design on PCB and simulationView attachment 177048View attachment 177049

If you want, you can also post your PCB layout at https://www.pcbway.com/project/ Along with the suggestions everyone has made here, you may get some suggestions about what else should be corrected and why.

 

[crutschow]

Sounds like either the rectifier bridge is incorrectly connected, or one of the rectifier inputs is grounded.

I suggest you add a resistor in series with the pot, so you cannot,
by turning the pot wiper, connect the adjust input to ground

Connecting the ADJ input to ground will cause no problems with the circuit.
The LM317 output will just go to its minimum of about 1.25V.