Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Most I/O boards offer open collectors, which I don't know what I would have a use for, but I sure can find a use for relays. Can I flip a relay with an open collector?
Most I/O boards offer open collectors, which I don't know what I would have a use for, but I sure can find a use for relays. Can I flip a relay with an open collector?
Yes, you simply wire the open collector output pin to one of the relay coil pins, the other relay coil pin wires to a positive voltage source. You need to find out the maxium voltage and current specifications for the open collector output pin and size your relay coils resistance and operating voltage to be within those specifications. It's also normal to wire a diode across the coil pins in reverse bias direction so as to snub transient voltages when the coil is de-energized.
You can switch pretty much anything with an open collector output, as long as it is within the parameters of the device. They're also good for switching a higher than logic voltage too. ie 12v 24v etc.
You can switch pretty much anything with an open collector output, as long as it is within the parameters of the device. They're also good for switching a higher than logic voltage too. ie 12v 24v DC etc.
Absolutely remember the diode across the relay coil (cathode toward the positive voltage) or your open collector output will end up being a shorted collector output or a forever-open collector output. Relay coils can develop hundreds of volts of CEMF when coil current is suddenly removed.
I would like to run some 110VAC devices from the open collectors, can someone point me in the right direction for some relays to get?
There are a zillion relays avalible but you need to give a few specification to select one. What is the load draw, that is what is the highest current draw (including surge) that you wish to switch on the 110vac side of the relay, as that defines what you need for the relay's maximum contact current ratings. What value DC voltage will you have avalible for powering the relay through the open collector outputs, 5vdc, 12vdc, 24vdc, etc ? What ever value of DC voltage you select, it will have to have a current capacity to be able to power as many relays as you will be installing, so how many relays do you wish to be able to power on at a time?
Also can anyone shed some light on the kind of resolution I can get on the analog inputs and on the analog outputs?
The analog A/D convertor is list as a 10 bit, so the resolution is one part in 1024. So if configured for 0-5vdc input then the resolution step size is 4.9 millivolts and double that if using the 0-10vdc input option the board mentions. The analog output D/A convertor is listed as 8 bit resolution so that is one part in 256 steps or 19.5 millivolts per step for 0-5vdc input or double that step size for 0-10vdc input option.
Hey Lefty, thanks great answers on the resolution.
I would LIKE to run it through my PC powersupply so 12V ~300-500watts, I'd like to be able to run all 8 at once and some items will pull up to 250 watts (lights), but most will be in the sub 50 watt range. All at 110VAC, so I guess I'd need 2.5 Amp and 0.5 amp relays.
Hey Lefty, thanks great answers on the resolution.
I would LIKE to run it through my PC powersupply so 12V ~300-500watts, I'd like to be able to run all 8 at once and some items will pull up to 250 watts (lights), but most will be in the sub 50 watt range. All at 110VAC, so I guess I'd need 2.5 Amp and 0.5 amp relays.
Alright plans have shifted a bit. I'm planning on using an Arudino. It has 14 digital I/O, could i use the 5v out to flip relays w/? Provided I used a diode across the relay? How much would opening all 8 relays cost in terms of amps?
The Arudino doesn't have output buffers so I doubt you'd even be able to trigger 1 with it directly, I didn't see any reference to the relay you're going to use but I skimmed through the post. You should be able to add a single transistor and resistor to the output of the I/O lines to drive your relays though very simple. I/O line goes through a 1k resistor to a transistor that will supply the actual coil triggering current. Any general purpose switching transistor that's rated for the amperage of your relays primary coil will work.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
