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Topic: Connect Two 100A SSRs Arduino Uno Power  (Read 522 times) previous topic - next topic

CD_Q

Right:  electromagnet guy says;

"You should be starting with all power below 40 V, preferably 12 V, start with coils of somewhat fine wire (14 ga) and many turns, ... will get you close to 1 T instantaneous pulse, and you can do that with maybe 100 turns at 10 A and 10 V, like a car battery."


I don't want to use a car battery though and am hoping to just plug it into the wall.

So 10 amps on/off a few times a sec.  how do I connect the arduino, wall plug, 2 EM set ups; mosfet and secondary unit that can handle 10amps to the 2 electromagnets?

JohnRob

Quote
wall plug, 2 EM set ups; mosfet and secondary unit that can handle 10amps
I'm not sure how you differentiate the "wall plug" and the "secondary unit"


You will need a 120VAC to 10 or 12V that can supply nearly 30 amps and be protected from short circuits.



Quick calculation:
If your coil diameter is 6" and you have 100T of #14.  Then DC resistance is approx = 0.42 ohms

Then at 12V the current will be 12 / 0.42 = 28 amps


Please do not PM me with thread based messages.  If your thoughts are worth responding,  the group should benefit from your insight.

CD_Q

I'm not sure how you differentiate the "wall plug" and the "secondary unit"

earlier in the conversation it was suggested ...
... drive the MosFet with an optoisolator (like a 4N25), this will keep the high current isolated from the Arduino, this will reduce your headaches in the long run as coils tend to generate voltage spikes that would otherwise be hard to suppress at the Arduino.

I was thinking a "secondary device" would mean something like the suggested 4N25, to ...keep the current isolated from the Arduino...  but Im using the usb port and will connect to a computer to set the controls.  BUT I do like the idea of something to help keep the high current isolated from the Arduino. 

As for the info I learned regarding the electromagnets - here is the message I received:

"You should be starting with all power below 40 V, preferably 12 V, start with coils of somewhat fine wire (14 ga) and many turns, and use very short pulses that disconnect after the pulse. At MagLab, we have a demo aluminum disk that is launched 15 feet electromagnetically with a pulse from 12 V. The disk has a hole in the middle because the launcher is a coil wound around an iron pole to get a lot of flux. Saturating the iron will get you close to 1 T instantaneous pulse, and you can do that with maybe 100 turns at 10 A and 10 V, like a car battery."

He's the director of the National High Mag. Field lab. 



And I'm trying to make sense of it all - What parts to buy and how to connect them.

So the parts, my only requirements are that I use a wall plug(whatever V is best, whatever will work) and that I use the Arduino Uno(to connect the usb for the controls).

Then what I don't know: Use a MosFet?  which part number, which one should I buy and how do I connect it, what wires do I get to connect the parts?  The SSR I showed earlier has power connect directly to the SSR module and avoids the Arduino.  Is that what I would need to do for the MosFet?  And how do I connect power to the Mosfet and then connect the MosFet to the Arduino?  OR how do I connect the MosFet to the Arduino, etc.

Im hoping when can continue the conversation anyway, Im learning a little more each time.

JohnRob

When you are learning like this it is best to take thing is small sections.

I suggest you get some #14 AWG wire and make a coil.   Ideally you would like "enameled" wire like one would use in a transformer but to start I would go to my local Home Depot or similar and purchase some #14 wire.  How much wire to purchase? see below

Coil:

Do you know the shape of the coil? (i.e. tall and thin or all bunched together etc)
Do you have an estimate of the diameter you need?

Once you get these then calculate the length and buy 25% more.

Wind your coil and connect it with a heavy switch or simply by hand.  But be careful when you de-energize the coil the collapsing magnetic field will create a high voltage on the coil wires that will shock you if you are holding the copper part of the wires.


How will you know if you are getting close to your 1T goal?


There are several magnetic circuit calculators on the internet you might try one of them to get a starting point for the coil design.



Please do not PM me with thread based messages.  If your thoughts are worth responding,  the group should benefit from your insight.

CD_Q

Thanks I figured I need to start there now too - Im looking for someone to wind the coils for me.  I have the info given to me regarding the rail gun at the national high mf  lab;  1T, 14awg wire, 100 turns and 10V - I'll see how far I can get with that.  And thanks for the advice regarding the magnetic circuit calculator.  I'll find that next than I'd suppose which MosFet to use after that.

I'll be back - EMs are spendy so this is gonna take a couple weeks to scrounge that up.

Thanks

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