12V DC Power Supply

[Windy Miller]

Guys, I need a 12v DC power supply to run a car heater blower motor for the forge. Up till now I have been using an old PC power supply that works fine, but it's not man enough to run the blower on the highest speed - it just trips the over current thingy inside and it shuts down.

I have a car battery that runs it ok, but I'd like something mains operated. I'm worried that a gassing battery and an open flame will cause a fire.

Any suggestions?

 

[the snooper]

have you thought about buying a transformer of the size you require and a bridge rectifier to make your own

 

[sardine]

How many amps do you require to start the blower ?

I've got a big crate of assorted power supplies .

 

[Windy Miller]

have you thought about buying a transformer of the size you require and a bridge rectifier to make your own

Actually no! I'm happy to give it a try though. Not that I know too much about that sort of thing!

How many amps do you require to start the blower ?

I've got a big crate of assorted power supplies .

Not sure to be honest. I'll stick a meter on it and see, but I'm not sure I'll be able to catch the starting rush.

 

[the snooper]

Actually no! I'm happy to give it a try though. Not that I know too much about that sort of thing!



Not sure to be honest. I'll stick a meter on it and see, but I'm not sure I'll be able to catch the starting rush.

if I remember most pc power supplies were 5 amp output so you may need to double it

 

[Robotstar5]

Have a look at CB power supplies, plenty on Fleabay.

 

[Pete.]

I have a pretty hefty 12v supply I'll check the output.

 

[Barking Mat]

Model railway train transformer?

 

[the snooper]

Model railway train transformer?

that will only be a very small output

 

[armalites]

The battery doesn't need to be anywhere the forge if you use some decent cable. You could then have the battery on charge somewhere else or even outside. You could even put a little solar panel on it to keep it topped up.

 

[RaceDiagnostics]

Your blower will probably be about 10 to 15 amps so a beefy power supply will be needed as you will want it to be running well within its specs and not really hot, so a 20A psu is what you should look for.

Something like this https://www.amazon.co.uk/Domire-transformer-Adapter-supply-Output/dp/B00CDHAF8U

Alternatively just keep a trickle charger on your battery and stay with that.

 

[graffian]

Try a more powerfull PSU, I run a mondeo rad fan from a 400W atx psu.
The starting current was easy to get over, I used a resistor and a couple of
relays, you switch the fan on and then switch the second relay.

 

[eSCHEn]

A 20A 12VDC power supply is under twenty quid from the bay of evil Windy. They're fanless and therefore silent until 20/25A.

First one I saw: http://www.ebay.co.uk/itm/DC-12V-24...er-Supply-for-LED-Strip-CCTV-UK-/291087849273

 

[atomant48]

I bought one of these to test some car stereos and amps. I looked at the other ones suggested but didn't want bare wires with kids about. This one has been great.

http://www.ebay.co.uk/itm/Logic-RC-...201ADJT-15amp-Adjustable-5-15V-DC-RC-Charge-/

 

[Windy Miller]

Problem solved!

I put the meter on the it, and although its max current rating is 10A, it showed that it was pulling about 15A on startup. This dropped to about 5A once it was running though, which the psu is easily capable of.

I looked online at the wiring diagram for the car (Citroen Saxo) and I saw that the three motor speeds were obtained by simply switching in and out a couple of resistors.

Once I realised this, I figured it was possible to avoid the startup current draw by running the blower on the mid speed, and then simply link across to the full speed connection and bypass the resistors. I've not tried it using the proper switch yet, but it certainly works when I just short out the connections. As suggested above, I could achieve this using a relay, but if I'm quick enough on the switch I may not need it!

As always, many thanks for all the advice. All I need to do now is to wire in the switch and see how it performs.

Thanks one and all!

 

[knighty]

you're already sorted now but it might help someone else...

you can get a server psu on ebay for about a tenner, they're 12v only (literally just 2 connections, 12v positive and negative)

most are about 40amp

you'll have to join a couple of pins together to get them to turn on.... but if you're happy doing as PC psu this is just as easy :-)

 

[Windy Miller]

That's a very good tip. I'll have to see what's laying around at work!

 

[knighty]

also (I should have said) if you want higher voltage... you can pop the cover off, cut the ground wire going to the circuit board (google fire exact location on your psu) and then put a bunch of them in series

I've got 8 serup in series to charge my electric bike @96v 40amp

never really used it in anger, but it always worked well, and it cost about £90 all in vs £700+ for an off the shelf 40amp charger