12v transformer for testing

[DKL]

I've just rebuilt the eas compressor for my old range rover so I figured I should test it before putting it on as I haven't touched the motor.
Rigged it up to a 12v transformer (well and old scalectrix one)and found the compressor would run then stop, run then stop.
Bugger thought I but the more I thought it didn't sound as though the rebuilt bits were sticking, it just stopped. So I put a meter across the transformer and usually a solid 14v or so. This dropped to 4v when the compressor was running but dropped to 0 when it stopped.
So I figure the problem is the transformer not the compressor. To be fair its years old and has lived in the shed.

So to the point. Unless I have missed some salient law of electrickery that would cause the above (quite possible) it would be useful to have a mains transformer that allowed things to be hooked up to it to test it.
I could just use a big battery but I'd like something a bit neater.
So what? If I google 12v transformer all I get is pages of lighting.

[andyiley]

That transformer will not be able to provide enough current to power a 12v compressor, you are lucky it even starts the compressor turning. As soon as the compressor starts to pressurise it will stall & could well blow up the transformer.

I suspect the miniscule motors for 2 x Scalectrix cars probably pull 1/2 amp, but a 12 volt compressor for a RR, would probably have a 20 amp fuse in the circuit on the car.

[sparkythecat]

Instead of transformer, Google 12v PSU, but with heavy current draw automotive components such as compressors and starter motors you're better off with a battery and heavy leads

Edited by sparkythecat on Thursday 5th March 21:18

[Dave^]

Some CTEKs have a direct supply mode, the 10A one and upwards I think...

[DKL]

andyiley said:

That transformer will not be able to provide enough current to power a 12v compressor, you are lucky it even starts the compressor turning. As soon as the compressor starts to pressurise it will stall & could well blow up the transformer.

I suspect the miniscule motors for 2 x Scalectrix cars probably pull 1/2 amp, but a 12 volt compressor for a RR, would probably have a 20 amp fuse in the circuit on the car.

I see, makes sense. The compressor isn't actually attached to anything so it is just turning the piston really. I did wonder about the amp side of things but its all I had.
Thanks

[ch427]

12 volt higher current power supplies can be expensive, if it were something you needed often it would be cheaper to rig up a battery and trickle charger under your bench or tucked away somewhere.
You could then run a set of leads to a test point on top of a bench or similar.

[DrDeAtH]

Why not just use a car battery????? Its 12v and will have plenty of capacity.

Normally found under the bonnet....

[buzzer]

Have a look at this artical.

http://www.autospeed.com/cms/A_111380/article.html


In fact, it's quite an interesting site!

[andyiley]

I doubt that will do what the OP is asking either, it MAY turn the compressor motor if it is unattached to the compressor.

[buzzer]

andyiley said:

I doubt that will do what the OP is asking either, it MAY turn the compressor motor if it is unattached to the compressor.

yep, I think you are right, guess it depends on the current draw, but anything with a motor is probably too high for that. Battery it is then!

[sparkythecat]

Love that Autospeed site that you've linked to buzzer.
There's loads of stuff on there to keep you busy in the Man Cave.

[buzzer]

sparkythecat said:

Love that Autospeed site that you've linked to buzzer.
There's loads of stuff on there to keep you busy in the Man Cave.

Yes, I have used several of the articles on there to make stuff for the car and the garage

last year I used that little module with the photo cell on it to link to the Solar Power on the house... when the brightness of the sun reaches a certain level, it switches the immersion heater on via a relay... saves all that electricity going to the grid. free hot water all last summer