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Electro-Magnetic Catch

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sirbrandon

sirbrandon

Mechanical
Jan 4, 2009
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Hi, I bought some of these magnetic catches (part number MGSR1: OFF when attracted), but I'm having trouble wiring up one of these. I have a 24VDC 2.5A DIN rail power supply. Do I wire the leads directly to the power supply, because it does not seem to work the way I think it should i.e. the catch plate falling off when the power is turned on. Any ideas?

 
 http://files.engineering.com/getfile.aspx?folder=072bd28b-5d5d-4b5b-9aa5-99698545370e&file=MGSR1.PNG
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Didn't appear to me that polarity should matter given that the part came with both leads having the same color. Nevertheless, I just gave it a try, and switched the wires around, but nothing happened. The data sheet mentioned Max ON/OFF Voltage of 100VDC, so I gave it 24VDC. Nothing.
 
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Give it a higher voltage (rated 100 VDC, you're only giving it 24 VDC)? Maybe, it's residual magnetism keeping the plate on and you need some force to remove it.
 
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Doesn't Off when attracted mean that it is supposed to release when power is applied? Perhaps it is working exactly as intended. Does the catch plate attract with the power off?

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
 
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It's unlikely, now that I think about it, that an open-loop electromagnet function could EXACTLY counter the PM magnet such that the attracted plate would be "falling off." It's much more likely that the attraction is simply, but substantially, reduced, so you should be measuring the how much force is required to detach the plate given a range of currents in the electromagnet. I suspect that you'll have to "tune" the electromagnet current to get an optimum countering of the magnet.

TTFN
I can do absolutely anything. I'm an expert!
homework forum: //faq731-376 forum1529
 
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The datasheet is all there is. When the power is off, the catch plate is attracted. So in theory, when power is supplied, the plate should fall off. I'm using a standard 24V power supply, probably need to go higher.
 
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Again, the magnet is a fixed value of attraction, while your voltage and current inputs are variable. Unless you get the coil to exact cancel the magnet's pull, the plate won't fall off, but if you're at least close, you should be able to pull it off with minimal effort, as opposed to pulling it off with no power applied.

TTFN
I can do absolutely anything. I'm an expert!
homework forum: //faq731-376 forum1529
 
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To elaborate on what IRstuff said, that device must have a permanent magnet in it to hold the plate with no power applied. The power has to go to a coil that creates a field to cancel the permanent magnet and delatch. That coil is rated at 100 volts, so this must be what is required to get full delatch. At 24 volts you have only reduced the latching force by 24 of 3 kg.
 
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