I'm working on a project to wire up a pipe organ's windchest using an Arduino as the backing system.

I'm looking to wire up about 400 outputs worth of solenoids that draw about 100mA of current at 14V each. I have a power supply that can handle this.

What I'd like to do is to create a system with an Arduino and something like a MAX7221 to be able to drive a lot of outputs with only a single Arduino. Obviously with those current requirements I'll need to use MOSFETs or something similar if I'm going to know with a MAX7221.

Besides spinning my own board with a MAX7221s and a diode matrix of MOSFETs are there any other good solutions to help keep costs and complexity down?

  • \$\begingroup\$ 1) I'm not familiar with pipe organ's, what are the loads? Are relays really necessary? 2) Product recommendations are off-topic here, might want to rephrase the question or it will be closed. \$\endgroup\$ – Wesley Lee Oct 5 '17 at 4:23
  • \$\begingroup\$ The relays are needed, there's air pressure behind the valve and the valve is actuated electronically. The relay and valve are all one component. \$\endgroup\$ – Jessie A. Morris Oct 5 '17 at 4:28
  • \$\begingroup\$ @WesleyLee I've also edited to change from a more product based question. \$\endgroup\$ – Jessie A. Morris Oct 5 '17 at 4:30
  • \$\begingroup\$ @WesleyLee As I was falling asleep last night I realized that I meant solenoids, not relays. \$\endgroup\$ – Jessie A. Morris Oct 5 '17 at 16:16

You can use IO Expander. There are tons of IO expanders that communicates with either by SPI or I2C with your microcontroller. Advantage is there many which can handle 250mA per channel. For example TLE94112ELXUMA1 provides you 12 outputs and you can directly drive relays with it.

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