Simply Power Supply Question

Thread Starter

liamstears

Joined Jan 31, 2013
26
Hi all and thanks in advance for any help

I plan to build circuits based on the attached but the fundamental difference being my input voltage will be 12v and not 24v. Basically I need to know what changes I should make to make sure I don't run into any problems.

I believe R1 and R2 of the "SUPPLY PCB" would need to be changed but what to exactly? And what type of diode/rating should they be?

Also wondering about the diode on the "IN PCB", I plan to make multiple supply PCB's all powered from the 1 in PCB and total output current on the 9v outputs could be anywhere between 2A and 6A

From my limited electrical knowledge I would assume the rest will be ok as it?

Thanks again

EDIT: I will be using a 7809 for 9v output
 

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MrChips

Joined Oct 2, 2009
25,931
You are going lower on input voltage. That will reduce the amount of wasted power. I would replace R1 and/or R2 with a wire jumper.
 

dl324

Joined Mar 30, 2015
14,323
I plan to build circuits based on the attached but the fundamental difference being my input voltage will be 12v and not 24v. Basically I need to know what changes I should make to make sure I don't run into any problems.
powerSupply.jpg
In my opinion, the RC filtering isn't required. If the input is 12VDC, the capacitors in the filter stage can be a few hundred uF with a 16V rating. D1 is unnecessary with a DC input voltage; unless you're worried about reversed power connections. The polarity inversion protection on the output doesn't make sense. It would make more sense to put it in the circuit being driven.

In the future, I'd advise you to avoid using schematics drawn by people who don't know how to draw them. We don't have text overlapping components or wires and three of the ground symbols are redundant.

Professionals don't use colored schematics. If the author had printed the schematic instead of doing a screen capture, the origin markers on the text wouldn't be printed. We use C as designators for capacitors, not E or F.
 

Thread Starter

liamstears

Joined Jan 31, 2013
26
Thanks for the replies, I will remove R1/R2 from the supply PCB

Diodes are to be kept for the reason of reversed power connections

What about D1 on the "In PCB"?

These circuits need to be protected as much as possible as they need to be robust
 

sghioto

Joined Dec 31, 2017
3,061
I plan to make multiple supply PCB's all powered from the 1 in PCB and total output current on the 9v outputs could be anywhere between 2A and 6A
Do you mean 5 volt outputs? Just a note each board can handle only 1 amp as designed.
If you keep D1 it needs to be rated at 10 amps, 50 volt min. Or remove D1 and install a 1N4001 on each board at the input.
 

Thread Starter

liamstears

Joined Jan 31, 2013
26
Do you mean 5 volt outputs? Just a note each board can handle only 1 amp as designed.
9v outputs using a 7809

Why only 1A? I planned to use heatsinks so the 7809 can handle increased load, the most load would be about 1.5A on a single 7809 board...

EDIT: I mean between 2A and 6A across multiple boards, as above 1 board max would be 1.5A, others will be below 300ma
 

dl324

Joined Mar 30, 2015
14,323
Diodes are to be kept for the reason of reversed power connections
How do you think the diodes on the output protect from reverse polarity?
What about D1 on the "In PCB"?
If the input is DC, D1 would protect from polarity reversal on the input. If the input can be AC, D1 is required for rectification.
These circuits need to be protected as much as possible as they need to be robust
Why? Are you expecting them to be used by idiots? It would be better to use polarized connectors to make them idiot-proof.
 

LowQCab

Joined Nov 6, 2012
1,931
Is this an Automotive application ?, or, what type of Main-Power-Supply are You using ?

What type of device(s) are You powering ?,
9-Volts at ~6-Amps seems very unusual, and there are better ways to accomplish that.

Is Current-Limiting desirable ?, ( it usually is ).
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Thread Starter

liamstears

Joined Jan 31, 2013
26
How do you think the diodes on the output protect from reverse polarity?
If the input is DC, D1 would protect from polarity reversal on the input. If the input can be AC, D1 is required for rectification.
Why? Are you expecting them to be used by idiots? It would be better to use polarized connectors to make them idiot-proof.
Yes I'm expecting it to be used by idiots lol

I just need a robust and capable unit that is protected as much as possible and open to any solutions


Is this an Automotive application ?, or, what type of Main-Power-Supply are You using ?

What type of device(s) are You powering ?,
9-Volts at ~6-Amps seems very unusual, and there are better ways to accomplish that.

Is Current-Limiting desirable ?, ( it usually is ).
.
.
.
This is a household application, I will be using a high amp 12v mains switch mode dc supply

Powering multiple 9v units that have various current requirements, current limiting is not necessary however most wont need any more than 300-500ma but 1 will need around 1.3-1.5a


I thought the original design would fit my needs but please anyone that has recommendations please give them, also recommendation on the first D1 on the "IN PCB" would be welcome

Thanks again for all the replies
 

dl324

Joined Mar 30, 2015
14,323
Yes I'm expecting it to be used by idiots lol
How do you think the diodes on the regulator will protect from a user connecting something backwards? If the circuit connected has integrated circuits, the regulator will pump as much current it can into a forward biased diode in the IC until the regulator current limits or goes into thermal shutdown or the IC opens internally.

And why 3 diodes in parallel? It's a screwball design. You'd be better off just consulting the regulator datasheet.
 

LowQCab

Joined Nov 6, 2012
1,931
"Multiple-Units" is not a number,
can your Power-Supply easily provide more than adequate Current for all Loads, all at once ?

What is the exact Output-Voltage and Current-Rating of your Power-Supply ?
.
.
.
 

Thread Starter

liamstears

Joined Jan 31, 2013
26
How do you think the diodes on the regulator will protect from a user connecting something backwards? If the circuit connected has integrated circuits, the regulator will pump as much current it can into a forward biased diode in the IC until the regulator current limits or goes into thermal shutdown or the IC opens internally.

And why 3 diodes in parallel? It's a screwball design. You'd be better off just consulting the regulator datasheet.
I am no electronics expert and certainly don't claim to be

Happy to hear any suggestions or other potential solutions, the datasheet is very simple for this

I am sure the designer of this circuit had reasons but I cannot answer why

If you have any other idea's or better idea's my ears are open and suggestions are extremely welcome

Thank you
 

Thread Starter

liamstears

Joined Jan 31, 2013
26
"Multiple-Units" is not a number,
can your Power-Supply easily provide more than adequate Current for all Loads, all at once ?

What is the exact Output-Voltage and Current-Rating of your Power-Supply ?
.
.
.
I'm sorry, I am building for around 14 units but possibly more in the future

12v 10a is the power supply I planned to use, regular usage would be 1.5-3A on the 9v outputs in total but would like to build it robust enough that it could handle up to 6A...
 

Thread Starter

liamstears

Joined Jan 31, 2013
26
As I posted earlier install an input diode on each board. Use a 1N5408, rated 3 amps.
Does this 12 volt supply have a control to fine tune the output voltage?
So I should replace the 1n4001 on each board with the 1n5408?

It doesn't, it's a fixed voltage
 

MrChips

Joined Oct 2, 2009
25,931
You don’t need D1.

For low loads, less than 1A, use regular 7809 with 1A current capacity.
For higher current loads, use a regulator with a higher current rating.
 

Thread Starter

liamstears

Joined Jan 31, 2013
26
You don’t need D1.

For low loads, less than 1A, use regular 7809 with 1A current capacity.
For higher current loads, use a regulator with a higher current rating.
Thanks for the reply

I thought the 7809 was fine for 1.5A loads? What regulator would you recommend?
 
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