[marting]

Hi To all,
I'm in the process of slowly building my 5 axis CNC router and have started wiring the control box. In order to control pneumatic valves and relays. I'm using an 8 channel relay module optocoupler which onboard relays are rated 5V and the breakout board (HDBB2 from CNC Drive) output voltage is 12V. My difficulty is that since there is no information on the optocoupler, I'm not sure if connecting as indicated on the attached circuit would damage the optocoupler. Is there anyone that can advise in this regard or has any experience with this type of optocoupler?
Thanks
Marting

[Al_The_Man]

You may have to reverse engineer the resistor used in the opto coupler, but as a general rule if the opto input is designed for 5 input, and you have 12v, then it may need a series resistor on each input, double the value that is there now, or look up the max diode current rating of the opto.
Also what is the nature of the BOB output?
Al.

[marting]

Hi Al,
I think so as well but thought maybe these would be tolerant enough, anyway I still have an alternative to connect it to the UC300-5LPT motion controller which has a 5V supply on each of the remaining 3 LPT ports. I'll actually be driving 2 HDDB2 BOB, in turn connecting 6 servos (slaving A axis to X axis), 6 homing sensors, 6 encoders and 2 TTL outputs, 1 for router speed control and another for laser control.

[CNCMAN172]

Most of these type boards will accept an input voltage to the optocoupler from about 3V to 28V, they tend to vary depending on which opto they actually used. The output stage is being controller by a 5V relay. You can have the contacts of the relay do whatever you want since they have COM NC NO contacts all available. The input normally has a current limiting resistor, since you are just turning on the tiny LED inside of the OPTO to activate the transistor inside. This is how people interface higher voltage inputs to lower voltage boards, since using the opto to handle the high incoming voltage is totally isolated due to the OPTO and relay to the lower voltage required on the microcontroller.

Russ

[marting]

Hi Russ,
thanks for the input, agreed but what I meant was the optocoupler circuitry being supplied by a higher voltage while still operating the relays by connecting to the 3 pins at the upper right side, which is normally bridged to supply the optocoupler circuit. It is highly probable that the later would only operate at the same voltage of the relays.
Thanks

[CNCMAN172]

If you look at this page you will see the schematic for a typical input on this board. It shows the OPTO and the Relay circuit.

Russ



SainSmart 8 Channel DC 5V Relay Module for Arduino Raspberry Pi 3D Printing, Arduino, Robotics | Sainsmart

[Al_The_Man]

I see now by looking at the HDBB2 it has open drain mosfet output, so they would normally just sink to common so I agree, there should be no concern.
Al.

[marting]

Hi Russ and Al, thanks for the input. After further consideration, I decided that since I wouldn't have enough outputs on the HDBB2 boards anyway, it would be better to connect all outputs to one location in the UC300 and on the other hand would be easier since the output on the later LPT port is 5V as well.
Regards marting


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