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Topic: Connect Two 100A SSRs Arduino Uno Power  (Read 521 times) previous topic - next topic

CD_Q

The set up:  12V DC adapter to Arduino to 2 separate 100A SSR modules.


Wawa

Are you trying to switch 12volt DC electromagnets with these SSRs?
The SSRs are for AC only.
Leo..

Paul_KD7HB

If you ever have a project that uses the SSR at 100 amps, you very definitely need heat sinks for them.  There are SSRs for DC, but only pretty low current.

Paul

adwsystems

If you ever have a project that uses the SSR at 100 amps, you very definitely need heat sinks for them.  There are SSRs for DC, but only pretty low current.

Paul
I have found (and have one) for 25A. Caveat, its from China and haven't used it yet. I'll report back later. :D

JohnRob

If the application is DC could you not just use MosFet's.

I know you stated the SSR's are capable of 100A but what does your application require?



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outsider

#5
Oct 18, 2018, 07:17 am Last Edit: Oct 18, 2018, 07:26 am by outsider
Hope you're not expecting 100 A out of that wall wart.  :)
Tell us about those E-magnets, how many Amps?
BTW: The ' ~ ' symbol by the terminals means AC, not "adjustable strength".

JohnRob

BTW   If you use the AC SSR on a DC circuit, you will be able to turn your load on but you will NOT be able to turn it off.  You will have to disconnect the coil power to turn it off.

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

CD_Q

THANK YOU!

 
I AM BUILDING an induction launcher that can vary the strength and frequency of what is launched, a few times per second.

I am using two electromagnets, one to launch and the other to be launched. The strength needs vary from enough to be repelled to enough to lift 3lbs 1 foot high.

For the electromagnets I don't know the gauge of wire to be used or how many turns so don't know the area.  I want to focus on how many Amps I can even get and will use that for finding out the wire gauge and turns.




FOR NOW I need to focus on the relay, mosfets? were suggested - and yes I do believe I need DC amps for the electromagnets. 

Since Amps mean current and current is good I need to find out just how many amps I can work with the Arduino Uno and how to connect everything correctly.




I would appreciate some suggestions as for components.

Paul_KD7HB

Perhaps Barry's web site would be of interest"Barry Hanson

Paul

JohnRob

To energize a DC coil the Arduino is not the limitation.  The switch and powersupply are typically the limitation.   You should choose a MosFet that can deliver the current you want.   DigiKey has an excellent webpage for selecting MosFets.

I'll guess, unless you are using a car battery, your powersupply is likely the limit

Question, will you be controlling the coil current using PWM?

If NO then I would 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.



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

Paul_KD7HB

THANK YOU!

 
I AM BUILDING an induction launcher that can vary the strength and frequency of what is launched, a few times per second.

I am using two electromagnets, one to launch and the other to be launched. The strength needs vary from enough to be repelled to enough to lift 3lbs 1 foot high.

For the electromagnets I don't know the gauge of wire to be used or how many turns so don't know the area.  I want to focus on how many Amps I can even get and will use that for finding out the wire gauge and turns.




FOR NOW I need to focus on the relay, mosfets? were suggested - and yes I do believe I need DC amps for the electromagnets. 

Since Amps mean current and current is good I need to find out just how many amps I can work with the Arduino Uno and how to connect everything correctly.




I would appreciate some suggestions as for components.
The inductance of the coils, which you don't know, will severely limit how fast you can build up the current in the coils. The way everyone else does this is to charge very large capacitors to a high voltage and then discharge the capacitors through the coil. The high voltage forces the current while the inductance tries to limit it.  It all comes down to time constants.

Paul

CD_Q

Thanks!  I am thinking PWM. Thats mainly why I need the fluctuations w frequency and strength, I don't know exactly what I need just yet and want to dial it in on a computer first.

I like the idea of keeping the high current isolated though, but don't think I want a screen.  What else could I use for this?

And looking at the tool on the digikey site I need to know FET type - Drain to Source Voltage (Vdss) - Current

For current it's giving numbers like 1220A (Tc) - whats Tc? and 1220A seems like a lot.  

The Drain to Source Voltage has 6V - 4500V, Im guessing using the 12v wall plug adapter is fine then? idk.


Choosing the amps determines the electromagnets coil size, wire gauge and diameter.  So how many amps do I need at most than?  I don't think I need very many amps to lift 3lbs 25cm.  I have an equation for lifting an object but it seems to suggest the field determines the height at all times.  With a launcher I expect the object being launched to use some of the provided momentum.  So I need some help on the required Amps for lift/launching 3lbs 25cm.


CD_Q

So if I use mosfets how would I connect them to the Arduino, wall outlet for power and to each electromagnet? Can I get an electrical diagram.

And how many amps do I even need to lift/launch 3lbs 25cm?

Paul_KD7HB

So if I use mosfets how would I connect them to the Arduino, wall outlet for power and to each electromagnet? Can I get an electrical diagram.

And how many amps do I even need to lift/launch 3lbs 25cm?
Is everyone afraid to tell the OP he is designing this thing completely backwards?

You need to compute the energy needed per second to begin to lift his 3lb weight and to move it some distance, against gravity, in some unknown time.

Once you have the energy required for your project, then  you can compute the magnetic force needed to begin to move the object. Then realize as soon as it is a bit away from the electromagnet, the magnetic force is now reduced and more force will be needed to move another increment, and continue this process until 25 cm is reached.

Knowing the force required for each step, now you can compute the ampere turns required to generate this force. Knowing that, you can decide on the size of the wire that will handle the current and the insulation of the wires to withstand the heat generated.

Once that is all designed, you can begin to design the current supply for the coils.

Are you going to use some magnetic material for the wire turns to be wrapped around? If so, that will need to be considered in making the electromagnet.

Paul

JohnRob

As Paul_KD7HB said, I think your approach is orders of magnitude away from what you need.

The repeated reference to "wall warts"  tells me you don't have a feeling for the amount of power you need.

I suggest you look through a catalog of DC solenoids and see the amount of power needed to create force under optimum physical conditions.   Now consider that an electric field is reduced by the cube of the distance from the actual coils to the object you are attempting to move.

Now you said you wish to move 3 lbs 1 foot.  Look at the solenoids for force and stroke length.  You will find the typical stroke (i.e. movement) is far less than your desired 1 foot.


Next pickup up your wall wart (or any wall wart)  look at the amps it is capable of........ compare it to the current the solenoids you might find......see if you are close.


John
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