danjperron
Posts: 3392
Joined: Thu Dec 27, 2012 4:05 am
Location: Québec, Canada

Re: 12 v for driving electromagnets PCA9685

Wed Aug 21, 2019 11:14 am

Do you think this circuit is ready for run with the components:
Not using a breadboard!

All your 12V wire should be on single point bus!
All your GND wire should be on single point bus!

The reason is the current. Take the current of a single coil and multiply it by the number of coil!. You bread board will heat up and melt.

Long screw on a small metallic plate with terminal lug going to the each individual coil and source of the mosfet. Or use a small plain pcb with drill hole to solder all you wires for coil VCC and mosfet source. This will remove an voltage drop because of the current draw and equalize them.

perik
Posts: 28
Joined: Sat May 10, 2014 3:12 pm

Re: 12 v for driving electromagnets PCA9685

Wed Aug 21, 2019 12:27 pm

danjperron wrote:
Do you think this circuit is ready for run with the components:
Not using a breadboard!

All your 12V wire should be on single point bus!
All your GND wire should be on single point bus!
Sorry but what is a single point bus? :)

danjperron
Posts: 3392
Joined: Thu Dec 27, 2012 4:05 am
Location: Québec, Canada

Re: 12 v for driving electromagnets PCA9685

Wed Aug 21, 2019 1:05 pm

You will drive a lot of current from your power supply.

The wire from the power supply will be a big gauge to handle the amount of current or you will have multiple power supply with all the ground attached together.

If you look at an electrical panel the main wire are attached to a metal plate which distribute the power. This is what we call the bus bar. It is able to handle the high current and each circuit from the house are connected to it using a breaker. The bar will handle the current from the main to each breaker which will draw all the current from the main.


This mean that you can't use a breadboard to take care of the coil current. You need something stronger to distribute the power to the coil.

Use terminal block! Some have the lug connected together! This is the simplest way.

https://www.12voltplanet.co.uk/bluesea- ... 0-way.html

perik
Posts: 28
Joined: Sat May 10, 2014 3:12 pm

Re: 12 v for driving electromagnets PCA9685

Wed Aug 21, 2019 2:11 pm

Ok I understand. Thanks for the explanation. Im going to make this as a prototype and then solder the MOSFETs modules on a PCB and maybe basically everthing except for the electromagnet itself which I need to be able to move around a bit.

Here is an updated image. (Prettend the green teminal block is the 30 A terminal block you linked to)

Does this look right? Do you think it will work as below?
elektromagneter12v_5.png
elektromagneter12v_5.png (94.56 KiB) Viewed 131 times

danjperron
Posts: 3392
Joined: Thu Dec 27, 2012 4:05 am
Location: Québec, Canada

Re: 12 v for driving electromagnets PCA9685

Wed Aug 21, 2019 2:52 pm

It looks ok but if you put your Mosfet on pcb this is another level! No needs for a terminal block!

But this is way ahead.

First you should try with one coil and one mosfet and see how much current and how much heat it dissipate.

perik
Posts: 28
Joined: Sat May 10, 2014 3:12 pm

Re: 12 v for driving electromagnets PCA9685

Wed Aug 21, 2019 3:05 pm

Thanks a lot for all your help!

Yes I think I will start to solder two modules on a PCB and try with electromagnets and connect these to with this one. Just for prototyping.
https://www.electrokit.com/produkt/kopp ... l-chassie/

If the outcome is good I will solder this as well on PCB.

perik
Posts: 28
Joined: Sat May 10, 2014 3:12 pm

Re: 12 v for driving electromagnets PCA9685

Wed Aug 21, 2019 6:27 pm

and by the way. If I decide to lower the voltage to 5 or 6 volt it will work as well. I guess it is nothing really I need to change in the setup in the case of this?

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