Vending Machine Relay Cards

Hi Community,

I have found a lot of relay cards from vending machines and I try to use that with an arduino. What I know is that the boards using 5 Volt for the IC’s and 26 Volt for the thyristor’s. The connector has 26 pins (1-9 = Data; 14, 16, 18, 20 = Select(Clock); 12 = Output Enable) and this pins are inverted (with an MC74HC14A) and then they are connected to an MC74HC574A. But I don’t know which voltages I must use and how I can connect this to an Ardunino.

I tried already to send with an K8055 data to it but it won’t work.
→ Set Data Bits
→ Clk (Sel 0)
→ Clear Data Bits
→ Set Data Bits
→ Clk (Sel 1)
→ Clear Data Bits

→ OE

I have attached some images from the board. (or use this link and

Best regards

Try the sequence

~OE = Low (pull to GND) CLK = LOW Set Data Bits CLK = HIGH CLK = LOW

The ~OE pin will disable all outputs if it's high.

~OE = Low (pull to GND) Set Data Bits CLK = LOW delay where .... CLK = HIGH CLK = LOW