I bought a few solenoid (http://www.ebay.com/itm/12V-DC-3W-E...ectromagnet-Lift-2-5Kg-Solenoid-/190586717598) and connected it a 12V battery. The battery was getting slightly hot suggesting the circuit was working. however, i dont see any magnetic force. any helpon how to troubleshoot this?

 

That is how a typical lift/material handling magnet appears, what is the resistance? Did you try it on an automotive battery or higher capacity?
Typically when used as a lift magnet, it requires a reverse polarity shot also to demag.
Max.

 

I bought a few solenoid (http://www.ebay.com/itm/12V-DC-3W-E...ectromagnet-Lift-2-5Kg-Solenoid-/190586717598) and connected it a 12V battery. The battery was getting slightly hot suggesting the circuit was working. however, i dont see any magnetic force. any helpon how to troubleshoot this?

If it is of the PM/EM variety you will see (significant) 'force' only when the device is not energized...

Best regards
HP

 

Does that mean, I charge the device for a long time before I can see the effect?

 

What sort of battery are you using?

 

I am using a 12 V battery (http://www.amazon.com/Strip-GP-High...ef=sr_1_1?s=hpc&ie=UTF8&qid=1428846643&sr=1-1)

 

...Again What is the resistance of the magnet??
Max.

 

Does that mean, I charge the device for a long time before I can see the effect?

No... If it is indeed a PM/EM (i.e. permanent magnet/electromagnet) unit it will attract ferrous objects without power applied, whereas application of power (of correct polarity and current) will effectively 'cancel' its magnetic field. ----- On the other hand if the device is solely electromagnetic it will show only slight (residual) magnetism while non-energized, but become strongly magnetic with the application of power...

To summarize:
PM/EM: Power on => Magnetic field 'OFF'/ Power off => Magnetic field 'ON'
EM only: Power on => Magnetic field 'ON' / Power off => Magnetic field 'OFF'


BTW that's a very low capacity battery for your application!
It may not supply sufficient current for even brief operation -- in any event it won't last long... As per posts Nos 2 and 7 you should ascertain the coil resistance such that you will be cognizant of the current/power requirement..

Best regards
HP

PS: Please note that the eBay description of the magnet implies a current requirement of 250mA and, hence, a (nominal) resistance of 48 ohms...

 

I bought a few solenoid (http://www.ebay.com/itm/12V-DC-3W-E...ectromagnet-Lift-2-5Kg-Solenoid-/190586717598) and connected it a 12V battery. The battery was getting slightly hot suggesting the circuit was working. however, i dont see any magnetic force. any helpon how to troubleshoot this?

The solenoid requires 250mA @12V, you will not get anywhere near this current with that tiny 12V remote control battery.

 

Thanks so much. I will get a 12V battery with higher capacity and report back.

 

In order to lift a ferro-magnetic object the magnet must come in direct contact with the object. Only then will you experience the maximum lifting capacity.

 

This is an example of the cranes I designed electronics for!

As the magnet heats, the magnetic strength decreases.
Max.

 

Fabulous. This is the kind of thing my son wants to build for his science project. Do you have any tips on how to build a model version of this for his school project?

 

A very simple relay for the pick up condition, you may need a short reverse demag pulse if light objects stay attracted at the point of turn off/drop.
Max.