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12-15v in, 5V 300mA(Isolated)out, power supply?

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peterjm

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Could anyone lead me in the right direction to finding a schematic for this?

Im trying to build my own 12-15v input to 5V 300mA(Isolated)output, power supply. The challenge is the power going out must be isolated because one of the things its powering is a voltage meter that reads the source 12-15v coming in from an alternator.

Ive tried constructing a couple of the schematics i've found on the internet but cant find one that does exactly what I want.

I built this one but its 9v and only 1 mA out:
Circuit - Isolated Power Supply for Digital Panel Meters

I found another 5v one by Dave Johnson as well, but its only 30mA.

The closest thing i found was on EDN: Information, News, & Business Strategy for Electronics Design Engineers. It converted 48V to 5V, 15W for use in telecommunication systems, but was alot more complex than the circuits I have made before and ran too high voltage input.

TIA for any suggestions anyone can give me!
 

Hero999

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peterjm

New Member
Reduce Standby Power Drains with Ultra-Low-Current, Isolated, Pulse-Frequency-Modulated (PFM) DC-DC Converters-µç×Óµç·ͼ,µç×Ó¼¼Êõ×ÊÁÏÍøÕ¾

Attached in PDF fromat, just in case the site goes down.
Attached Files
File Type: pdf Isolated Converter.pdf (563.2 KB, 2 views)
Id like to try and build that but it doesn't show the values / Product numbers.

For the effort required you're probably better off buying an isolated module like a Traco. Digikey sells these things.
For the Traco do you mean something like This? This looks very interesting.
I found a couple of kits at digikey like you suggested Here and Here

Ill order one and try it. Thanks!
 

blueroomelectronics

Well-Known Member
The Traco units work like a charm. Only drawback is cost but several manufactures make similar units so shop around. Also try Mouser.com
 

Hero999

Banned
Id like to try and build that but it doesn't show the values / Product numbers.
The data sheet for the MAX1771 gives typical values. It doesn't give exactly the same circuit but you can use it as a guide to fill in the blanks.

I agree with blueroomelectronics that using a DC-DC converter module is an easier option but it's more expensive. Also if this is an educational project you'll probably get more marks for designing your own solution.
 

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peterjm

New Member
I ordered a TDK-Lambda Traco unit and the first one was defective. Returned it and the second one worked great for what i need. The voltage numbers on the meter still jump around a bit more than id like them to but i think its just the soldering and inaccurate potentiometer i'm using on the circuit. Thanks for the info!
 

Hero999

Banned
Thanks for returning most people don't.

It sounds more like the ripple voltage is confusing the DVM than a problem with a pot.
 

Hero999

Banned
A mentioned in the other thread, the output is highly unlikely to be isolated from the input which is one of the main requirements of the origional poster.
 

tcmtech

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Most Helpful Member
What kind of meter is it?
 

Hero999

Banned
colin55,
Why did you have to delete your post after I responded to it?

Were you too embarrassed that you made a mistake suggesting that a cheap cigarette lighter powered 3V charger can be tweaked to give an isolated 5V supply?:eek:

Don't worry, we all make silly mistakes from time to time, it's normally better just to admit it rather try to hide it. If no one had responded then fair enough but I had responded so deleting your message was quite rude of you.
 
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