Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Adjustable power supply PCB design problem

Xlll

Newbie
Joined
Jun 23, 2022
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
22
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
IMG_20220623_210815.jpg
Screenshot (238).png
 

betwixt

Super Moderator
Staff member
Joined
Jul 4, 2009
Messages
15,526
Helped
5,026
Reputation
10,076
Reaction score
4,864
Trophy points
1,393
Location
Aberdyfi, West Wales, UK
Activity points
131,576
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

Advanced Member level 5
Joined
Mar 31, 2005
Messages
5,681
Helped
1,152
Reputation
2,316
Reaction score
1,220
Trophy points
1,393
Location
California, USA
Activity points
30,955
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

Newbie
Joined
Jun 23, 2022
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
22
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

Super Moderator
Staff member
Joined
Apr 17, 2014
Messages
21,994
Helped
4,591
Reputation
9,196
Reaction score
4,812
Trophy points
1,393
Activity points
145,219
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 ---

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
 
Last edited:

stenzer

Advanced Member level 2
Joined
Oct 1, 2012
Messages
639
Helped
106
Reputation
213
Reaction score
140
Trophy points
1,323
Activity points
6,836
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

Advanced Member level 4
Joined
Jan 25, 2019
Messages
1,000
Helped
217
Reputation
433
Reaction score
260
Trophy points
83
Activity points
7,513
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
 

LaTeX Commands Quick-Menu:

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top