Single ended spindle encoder (5i25+7i76)

Good afternoon! First time posting here & rather new to LinuxCNC (But not to Linux).

I've build my controller and everything bar the encoder seems to be working. Spindle motor turns nicely, but no feedback. Meanwhile, every time I hook up the encoder it blows up, so clearly I'm doing something wrong. Could this have anything to do with software configuration (I simply checked the single ended encoder option in PnCConf) or am I wiring it wrong?

The spindle encoder is very bare and simple: Two light barrier sensors (optocouplers) and a perforated disk. One with 100 pulses, one with 1 (Index). Now, I wired the mas follows down to 4 wires: +5VP from the 7i76 to diode #1 +, which is connected in series to diode #2 and then to ground on the 7i76. That same +5vp is connected to both the phototransitor + poles, whose negatives are connected as the signal of these to the 7i76 encoder inputs (A+ and IND+).

Cheers & sorry for the inconvenience.

Thanks for your response. The forward current is 60mA. A resistor would make a lot of sense.

Would it be okay if the resistor would be before the +5vp connects to both the LED and phototransistor? Would make it a lot easier to wire up.

It's two of KTIR0221DS . I'll have a try with 180 Ohm resistor on the negative.

Well, I have it wired this way currently, but still no success. Diodes did not die this time, however, so that points the problem elsewhere now.

Regarding the pull-up resistor, doesn't the 7i76 have internal pull-ups for all inputs? The current scheme is;

+5vp to to the + of phototransistor 1, 170 Ohm resistor to the + of the diode, in series to the next diode and to ground, the same +5vp in parallel to the + of phototransistor 2 and the - of both phototransistors to Encoder A+ and Encoder IDX+.

I'm seeing most phototransistors being hooked up differently though, so perhaps I'm doing it wrong. Should the negative of the phototransistor go to both ground AND the encoder input?

I'm using 12v for the field voltage and the cable is grounded, short cable. I'm not super worried about noise for now.

Thank you for your time.

No, I cannot. I'm thinking the phototransistor must be improperly wired, as now with the resistors the diodes ought to work just fine (Unless wiring them in series causes some issues, but I don't see how, it's no different from two LEDs). Both diodes still respond to a diode tester on a multimeter.

I have two thoughts currently:

1: Should the phototransistor + side go to both ENC + and ground?

2: Am I wrong connecting +5VP to the + of the phototransistor and into ENC +, alternatively being ENC + into phototransistor + and the phototransistor - to ground?