Controlling a 24V circuit using Arduino Uno R3 and 5V relays. - Page 1
Forum section: electronics / projects

author: sahil2211
author_rank: Newbie
timestamp: July 30, 2018, 03:47:49 am
content: Hi All,I'm a new user and very new to electronics. I'm working on an automation project in my factory and think I can use an arduino to operate pneumatic cylinders that work using 24V coils. I know how to program the arduino but not sure how I can usehttps://www.amazon.in/gp/product/B0795NSRYB/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=AHESUPTC6MZQV(relays) to control these coils. Will I need to use other relays (if yes then which ones?) or can I use something to manipulate the power?Looking forward to gaining knowledge.Cheers!

author: latonita
author_rank: Newbie
timestamp: July 31, 2018, 10:43:30 am
content: here is example:https://elementztechblog.wordpress.com/2014/07/21/interfacing-relay-boards-to-arduino/

author: Seekonk
author_rank: Super Contributor
timestamp: July 31, 2018, 01:28:33 pm
content: $430, sure that are not missing a decimal point after the 4? My personal feeling is you are asking for a shit load of trouble using 5V relays. The relays should operate off their own power supply and 5V relays are current hungry which means spikes in current. Without extreme care the micro will be . If your solenoids are DC, use a FET driver board.

author: DaJMasta
author_rank: Super Contributor
timestamp: July 31, 2018, 05:40:03 pm
content: Relays are basically magnetically operated switches, and while this sort of voltage could be done by transistor switching, I'd probably look towards relays too unless you need very fast switching, as relays could take 10s of milliseconds to switch or release. A board like the one linked will have optoisolators and a transistor to drive the coil, so logic level drive should be sufficient to turn them on or off (driving a relay directly often takes more current than a micro can usually provide), and by using a module like this, you don't have to worry too much about flyback diodes or snubbers as they should already be part of the design. If it were me, I'd also use a power inductor and large value bypass cap on the coil voltage input for the board, just to keep the switching noise and current draw out of your power supply. Also worth noting that each coil could be 50mA+ each when enabled, so make sure you're using more than just the regulator output on the arduino.If you're looking for long life, high reliability options for industrial use, I'd probably look towards a different module, as these are sort of the cheap Chinese hobbyist grade modules, but they should do well enough for the job in many cases. This sort of switching application is pretty common, so there should be MANY industrial options for control, even ones using built in controllers or small form factor computers.

author: latonita
author_rank: Newbie
timestamp: July 31, 2018, 07:52:12 pm
content: ha ha i think it is Indian rupees, about 6-7 US dollars.as for current sink - that board requires 15-20 mA per channel (opto isolated).if we are talking about arduino uno based on atmega328p - i think it can sink up to 200 mA, so even if topic starter will use all 8 channels - it will be okayhowever the quality of that relay module is under question, mostly relays themselves are under question