@Monty
Hi !

The EL-3 has two opto sensors just below each coin validator. Each opto receiver triggers a pulse back to the motherboard when the light from the transmitter is blocked by a coin passing between the transmitter and receiver. Since there are two transmitter / receiver pairs, two pulses that are slightly out of phase are sent back to the motherboard. These must fall within the predefined valid timing intervals described in the EL-3 manual to be accepted as valid credit pulses.

If the timing is wrong, or if just one of the optos are triggerd, the EL-3 won’t accept it as a valid credit pulse.

Modern coin validators normally transmits a single pulse or a pulse train to signal accepted coins. Beacuse the EL-3 has to receive two separate semi-parallell pulses to accept credits, it’s difficult to connect more modern coin validators to the machine.

This device serves as a signal converter / buffer that you can use to interface newer coin validators to the machine.

The operation is best described by an example. In Norway one would would probably want to use a coin mech that accepts 1, 5, 10 and 20Kr coins. One could be programmed to send one pulse pr 5 kr recognized, and the other to send one pulse pr 1 kr recognized. These would replace the coin comparators that are already installed in the machine.

Scenario:

0) The EL-3 expects 5 credit coins from the left validator and 1 credit coins from the right.
1) The player drops a 10Kr coin in the right validator.
2) The validator transmits a pulse train consisting of 10 separate pulses on one of its output pins.
3) The devices counts the pulses and waits for about 500 ms.
4) If no more pulses are detected, it starts retransmitting by simulating pulse pairs that fall within the timing parameters of the El-3
5) The El-3 accepts 10 valid pulses and the player gets 10 credits.
6) The player drops a 20Kr coin in the left validator.
7) The validator transmits 4 pulses
The device retransmits these 4 pulses
9) The El-3 accepts 4 pulses and the player gets 20 credits.

The device comes with a 16 pin IDC connector that snaps onto the flat cable that runs between the existing optos, and a connector with wires that you have to connect to the outputs from your coin mechs.

It’s almost plug and play, but a you have to be aware of a couple of things

a) You should not remove the original optos from the machine (I suspect that it runs a self test/diagnostic on them at startup).
b) The IDC connector has to be connected as described in the pictures (If tou connect it backwards, I suspect that blue smoke will start to appear somewhere …)
c) It leeches power from the cable, so you don’t need a separate power supply to run it.
d) It has inputs for validators with open collector outputs and validators that sends out voltage pulses. Be careful to check what kind of output your coin mech provides.
e) Input pulse width and timing is not critical. It has a timeout period of about 500 msek before it decides to start retransmitting credit pulses to the machine.

I have tested the device on an imported EL-3 and a couple of newer Comestero validators.

I hope this answers your questions. Let me know if you are interested.

Update: There’s now a new firmware version available. This retransmits a twin-pulse after each detected pulse instead of accumulating pulses in a buffer. The twin-pulse duration is now approx 8 ms. This allows for retransmits in between the pulses from the coin-validator. The pulses from the coin validator can be of arbitrary length, but the pulse separation must be greater than 10 ms (allowing for some processing time)
The new firmware is also testet with the original coin comparators (1 Kr, small coin with a hole in the center that normally would confuse the twin optos)

Har nå justert timingen bittelittegrann opp, slik at det ikke ligger helt på toleransegrensen. Pulsene inn til EL3 er nå 2,5ms