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Electromagnet trigger circuit help!

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DongBeetle

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Hi all
I'm new on this forum, and on electronics, which has been my new hobby for the past 2-3 months, and now I'm seriously considering an education within this field.
Anyway..

My dad gave me this task, to build a circuit that can trigger an electromagnet when a button is pushed.
Here's the circuit I've come up with.
electromagnet_switch_web.jpg

The circuit is ment to be used as the cutter mechanism, that will cut fishingline into 2" pieces. I expect it to be triggerd about 2-4 times/sec. at fastest phase.

My questions is:
Will this circuit work at all?
Does the different values of caps and resistors look ok?

If you wonder why anyone would cut fishingline into thousands of 2" pieces, it's for making fake shrimp eyes for use when making flys, for fly fishing.

Regards.
 
Hi,

Looks a little overly complex for what it has to do so far. For example, why the transformer...why not run everything off of 24v?
 
(why not run everything off of 24v?)
Well the relay I've got is a 12V, and I was thinking that using 12V might protect the components at little better, less current, heat ect.
And then using the 24V line to power the magnet coil, I was thinking that it would give a more powerfull kick!?
 
(why not run everything off of 24v?)
Well the relay I've got is a 12V, and I was thinking that using 12V might protect the components at little better, less current, heat ect.
And then using the 24V line to power the magnet coil, I was thinking that it would give a more powerfull kick!?

Hi

As drawn looking at a glance it looks like it would work. However, I have to agree with Mr. Al in that it would be more practical and simpler to run everything off 24 VDC. I have a 12 volt coil relay lying here on my desk from this family of Omron relays. If I look at the data sheet and DC coils I see the coil power is specified at about 1.5 watt. Coil current @ 12 volts is about 126 mA but the same relay with a 24 volt coil has a coil current of about 56 mA. Same power of about 1.5 watts so really as to heat there is no difference.

As to solenoids? Mechanical solenoids of the push pull family are rated by force. Much like relay coils the solenoid coils come in several voltages but within a model family they will have the same force specification. Therefore like a relay, a solenoid with a higher voltage coil won't give any more bang for the volt. Double the voltage and half the current or half the voltage and double the current, same power expressed in watts.

That is why I would consider running everything on either 12 or 24 VDC but not worry about added parts to use both voltages. Incidently, if you have not gotten a solenoid yet, McMaster Carr Supply is a good source to start with.

Ron
 
Why do you even need the relay? Or if you need the relay (because you cannot but a FET which will switch the solenoid directly), then why do you need the FET in your circuit?
 
Last edited:
Thanks for your replys!
I have to agree with you all, it is overly complex that first circuit I drew!

No I dont have a solenoid yet, and mcmaster.com looks like they have a lot of good stuff, but I've heard that ordering from outside the US these days, can be a nightmare and might never go thru.
But a good source in the EU must also exist!?

I wouldn't mind making the solenoid, so if anyone can tell me how to calculate wire gauge and number of turns needed for a 24V solenoid, I'll just wind my own :)

I found out that the 24V adaptor I'm gonna use for this project is DC already, so I've tried to do as you suggested, and simplyfi my circuit a bit.
electromagnet_switch_web2.jpg

So does this look more reasonable?
I decided to go for the mosfet as the solenoid switch, mostly because I have more IR530's and I need a relay in another project.
I'm still not sure about resistor and cap values, as I said I'm kinda new to all of this, and I haven't exactly been using math alot the last 10 or so years :)

Again thanks for the help.
regards.
 
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