12v DC Motor

[Ian S CParticipant @iansc]

The wiper motor I use for feeding the table of my mill runs forward, and backward with no problems, 18 volts is no trouble, these motors will take up to 24 volts.

Ian S C

[Ian PParticipant @ianp]

Posted by Ian S C on 27/11/2014 12:04:51:

The wiper motor I use for feeding the table of my mill runs forward, and backward with no problems, 18 volts is no trouble, these motors will take up to 24 volts.

Ian S C

Your motor must have better armature thrust arrangements than the majority of car windscreen wiper motors. Car manufacturers are highly ingenious as shaving the last fraction of a penny/cent off the cost of every component. In the long run simplifying and reducing the number of components is actually better for the customer, for as well as there being less to go wrong, they can spend the money and concentrate on better specs for the parts that are essential.

Most if not all wiper motors use a worm and pinion, neither gear will be bothered which way its rotating but In its intended application the motor armature end thrust is always in the same direction so the manufacturer caters for that properly. The armature end float in the non thrust direction might only be limited by a thin walled plastic sleeve (part of the rotor insulation). Its perfectly adequate when wiping but might not last long if the motor is reversed.

For reversing operations there is a much more suitable motor in the doors of modern cars. The window driving motor also has a worm and pinion reduction but it designed to be reversible.

Ian P

[Graham Williams 5Participant @grahamwilliams5]

Latest update Guys. Tried running the motor direct off the laptop psu at 18.5 volts (checked with meter) as Ian said but motor wouldn't run. Don't really want to buy an electric window motor with regard to the rotation question so will pin the extension shaft. Now I've finally managed to corner my neighbour who is a retired BT development engineer. He's saying that the design of these psu is not suitable for doing what I am trying to do, he did try to explain the technicalities but he lost me after 10 seconds or maybe not as long as that. As it runs off a battery charger he says use one of those, looks like Neil's suggestion! was the way to go, though he's going to see if he has a suitable transformer/rectifier/capacitor etc in his bits and pieces to build something up. If not will try to pick up the smallest charger in physical size with the necessary capacities that I can. Thanks for all the help and suggestions, really appreciated.

Cheers

GW

[Neil WyattModerator @neilwyatt]

The The motor will have very low resistance when stopped, and the PSU probably sees this as a fault and refuses to deliver current. A 12V motor I have here takes 7A when stalled, at 18.5V that would be over 10 amps when run off a low-impedance supply like a lead acid battery. The PSU will think it's been shorted out.

You need an 'unintelligent' PSU or a transformer based one.

Neil

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