I have purchased a 12v 8-channel relay board that I will be connecting to my arduino, powering some solenoid valves. The relay board i have bought is here. It advertises opto-isolation, however some users have disputed this. I also see one commenter says you can trigger the relays with the 5v from the arduino along with an external 12v power source for the components (solenoids) like this img ->
, but there seems some dispute on that as well. My question is, is isolation possible with this relay board, and if so is that wiring diagram correct (i understand the img is using the 5v version, i will be using the 12v).
EDIT: This is a another similar convo on the topic, but it seems the final solution was to modify the board with some resistors. Is this the only solution?
The amazon Q&A page seems to answer the question of isolation or not (yes there is). However im still shaky on the solution:
Q: "It looks like only 1 dc+gnd is available. are the relays completely isolated from the mcu?"
A: "you source the DC to those terminals then parallel your choice for control through your choice of external switching to the individual in1-8. yes, the are isolated ."
Do they mean run the 12v parallel with the relay NC (if set up that way) pins?
Paul_KD7HB:
Did you look at the schematic on the page you linked to? I shows opto-isolation.
Paul
yes i did and did not see an example of how to wire that relay board for opto-isolation. From what ive learned, it seems i need to be able to connect a 12v (to power the solenoids), and a 5v to trigger the relays. But there is only one place to connect power (DC+), unlike some other relay boards ive seen with a vcc and jd-vcc.
yes i did and did not see an example of how to wire that relay board for opto-isolation.
The inputs (and Vcc) go straight into opto-isolators (U1 - U6). It's isolated - There is no electrical connection between the LED-side of an opto-isolator and the transistor-side.
From what ive learned, it seems i need to be able to connect a 12v (to power the solenoids)
The relay coils need 12V. That power, and the ground for the 12V supply can be completely separate and isolated from the Arduino power supply. Or, they can share the same supply and/or the same ground but then there are not truly isolated.
And of course, the relay contacts are completely isolated from the relay coil, but again you can optinally make non-isolated connections. So depending on how you wire it, you can get "double isolation" between the Arduino and whatever is connected to the contacts.
and a 5v to trigger the relays. But there is only one place to connect power (DC+), unlike some other relay boards ive seen with a vcc and jd-vcc.
5V (Vcc) has to be supplied from the Arduino to get "complete circuit" on the LED-side of the opto-isolator. When the Arduino's output signal goes low, the opto-isolator turns-on. (There is no required ground-connection to the Arduino.)
12V (and an associated ground) is required for the relay coils. I assume the relays are marked "12V"?
DVDdoug:
The inputs (and Vcc) go straight into opto-isolators (U1 - U6). It's isolated - There is no electrical connection between the LED-side of an opto-isolator and the transistor-side.
The relay coils need 12V. That power, and the ground for the 12V supply can be completely separate and isolated from the Arduino power supply. Or, they can share the same supply and/or the same ground but then there are not truly isolated.
And of course, the relay contacts are completely isolated from the relay coil, but again you can optinally make non-isolated connections. So depending on how you wire it, you can get "double isolation" between the Arduino and whatever is connected to the contacts.
5V (Vcc) has to be supplied from the Arduino to get "complete circuit" on the LED-side of the opto-isolator. When the Arduino's output signal goes low, the opto-isolator turns-on. (There is no required ground-connection to the Arduino.)
12V (and an associated ground) is required for the relay coils. I assume the relays are marked "12V"?
If it works when connected like the drawing in post#0, then it can't be an opto isolated module.
(no current can flow if ony one wire is connected to the opto section)
Leo..
