How can I control 40 relays?

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mtbf0
 
Posts: 1645
Joined: Sat Nov 10, 2007 12:59 am

Post by mtbf0 »

i did this in the dim distant past to control an 8x8 rgb matrix with a pic18f252.

i reconsider your statement about the wires seeming right, since the only firmware change is changing a loop counter from 16 to 24.

meal
 
Posts: 11
Joined: Fri Sep 26, 2008 11:53 pm

Re: How can I control 40 relays?

Post by meal »

Thanks again for all your help everybody.

I have the circuit working now and thought I would share the solution.

I have 40 5v relays wired to 5 daisy chained 74HC595N Chips, controlled by an Arduino micro controller. For the control of 40 5v reed relays the ULN2803 chip was not needed.

The circuit worked when I connected the first chip to the last on the power rail, then connected the last to the ones in between.

wgrube
 
Posts: 3
Joined: Sun Aug 01, 2010 12:33 pm

Re: How can I control 40 relays?

Post by wgrube »

Like the 74HC595 you can use a CD4094 shift register.
I'm using a CD4094 shift register and BC548 transistors to drive 5V relays, works perfectly. The outputs from the 4094 are connected to the base of the BC548 through a 1k resistor, emitter connected to the ground, collector connected in series with the relay spool to +5V. A 1N4004 diode is connected in parallel in inverted position to the relay for protection. Using this configuration draws some current so I don't use the Arduino's power line to drive the relays, using an external power supply for that purpose.

iwansoenarto
 
Posts: 1
Joined: Mon Nov 04, 2013 4:11 am

Re: How can I control 40 relays?

Post by iwansoenarto »

Hello,

can you please share the detail diagram on this ?
thanks.

Rgds,
iwan
wgrube wrote:Like the 74HC595 you can use a CD4094 shift register.
I'm using a CD4094 shift register and BC548 transistors to drive 5V relays, works perfectly. The outputs from the 4094 are connected to the base of the BC548 through a 1k resistor, emitter connected to the ground, collector connected in series with the relay spool to +5V. A 1N4004 diode is connected in parallel in inverted position to the relay for protection. Using this configuration draws some current so I don't use the Arduino's power line to drive the relays, using an external power supply for that purpose.

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