I would like to control many (about 100) electromagnets. I'm going to use some shift registers to control the rows and columns.
My question is, how I can achieve to control the Mosfets that are connected to the coils.
can anyone help me?
Hi, give us a link to the spec of these electromagnets with the built-in mosfets.
You think you want to use shift registers, and your topic title mentions multiplexing. I am not saying that is wrong or right, but can you explain why? What will the electromagnets be used for and how many will be activated at once?
Paul
the electromagnets are not yet existing. I would like to arrange them in a 10x10 array. Do you know where I can get magnets from?
here is the link of a 4x4 array, driven by a shift register, for 10x10 it's simmilar
http://cdn.instructables.com/FMB/QE1Q/H32S08P4/FMBQE1QH32S08P4.LARGE.jpg
Instead of LEDs I'm going to add Mosfets at the end
maybe you have seen the ferrolic clock. There you have a ferrofluid thad is controlled by electromagnets. I want to create a such a display
the magnets need a high current so I think I have to use a Mosfet to turn the magnet on and off.
But because of the multiplex technoligy they only get a signal for a short time. So how can I convert this On-Off signal into a steady signal?
you can have a look at it here: http://www.ferrolic.com/
PS Sorry for my English
Once you multiplex the signal is always going to be on and off, that is the nature of time division multiplexing.
Are you sure that a single direction current pulse is going to work? What about the build up of a permanent magnet field in the core?
I would try just one magnet before you go buying 100.
Very cool video.
Mike is right, you need to experiment wuth one electromagnet. There are several questions that need answers before you can finalise the design.
You need to know if you need to keep the current on continuously or if you can switch it on and off rapidly witb a dudy cycle of, say, 1 in 8 or something like that, and have the ferofluid stay in place. If the electromagnet must be continuously energised, then you cannot multiplex. If you can multiplex, then you need transistors for each row and column, not each magnet.
You also need to know the instantaneous and/or average current needed in the coils to hold the fluid in place.
What voltage will the electromagnets need to run at? 5V? 12V?
If you only need to sink current, or only source current, I have 2 cards with 32 MOSFET drivers, one N-channel, the other P-channel, can use 3 and daisy chain them easily to control 96 magnets, no fooling with multiplexing needed.
Here is the N-channel, the P-channel is similar and posted in a topic from a couple of days ago.
http://www.crossroadsfencing.com/BobuinoRev17/
Shift in 4 bytes to the 74HC595s from an Ardiuno, the 32 outputs change accordingly.
The card is designed to have one amp per channel. The blue connectors are rated for 10 amps, so you need to connect in parallel to a supply.
The P-channel board is similar, with P-channel MOSFETs and TPIC6C595s to pull the gates low to turn them on.
http://forum.arduino.cc/index.php?topic=376507.0