# 2 channel relay board with 5V DPDT relay **URL:** \ **Category:** General Guidance\ **Created:** [January 10, 2021, 11:01pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793 "2021-01-10T23:01:42Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![french\_guy](https://avatars.discourse-cdn.com/v4/letter/f/e5b9ba/32.png) [@french\_guy](https://forum.arduino.cc/u/french_guy)\ **Post date:** [January 10, 2021, 11:01pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/1 "2021-01-10T23:01:42Z")
Hello Looking for 2 channel relay board with dpdt relay AND opto-isolation I can find relay boards that are opto-isolated but relays are spdt only > **[1pcs 4 Channel Relay Module 5V with optocoupler Protection 4 Way Relay Expansion...](https://www.amazon.com/optocoupler-Protection-Expansion-Development-microcontroller/dp/B07TG3ZHN7)** > > 1pcs 4 Channel Relay Module 5V with optocoupler Protection 4 Way Relay Expansion Board for MCU Development Board Supports AVR/51/PIC microcontroller with optocoupler Isolation: Amazon.com: Industrial & Scientific I can also find relay board with dpdt relays, but they are not opto isolated...! > **[Electronics-Salon 2 DPDT Signal Relay Module Board, DC 12V Version, for Arduino...](https://www.amazon.com/Signal-Relay-Module-Arduino-Raspberry-Pi/dp/B087T96XQT)** > > Electronics-Salon 2 DPDT Signal Relay Module Board, DC 12V Version, for Arduino Raspberry-Pi 8051 PIC.: Amazon.com: Industrial & Scientific Any links for boards that have both? Thanks ---
**Author:** ![gilshultz](https://avatars.discourse-cdn.com/v4/letter/g/67e7ee/32.png) [@gilshultz](https://forum.arduino.cc/u/gilshultz)\ **Post date:** [January 11, 2021, 1:13am UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/2 "2021-01-11T01:13:45Z")
That is a fairly specific part. If you are desperate you can get the opto isolator as a separate item from Sparkfun [SparkFun Opto-isolator Breakout - BOB-09118 - SparkFun Electronics](https://www.sparkfun.com/products/9118). That would drive the relay board you linked to. As far as two on one I do not know of any, ---
**Author:** ![TomGeorge](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tomgeorge/32/215261_2.png) [@TomGeorge](https://forum.arduino.cc/u/TomGeorge)\ **Post date:** [January 11, 2021, 7:37am UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/3 "2021-01-11T07:37:03Z")
Hi, Is there a reason you need opto-isolation? The relay provides the isolation from the input to the output load current. The non opto PCB will have all the back EMF protection diodes that the opto isolated PCB will. Thanks... Tom.. 🙂 ---
**Author:** ![Paul\_B](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/paul_b/32/216376_2.png) [@Paul\_B](https://forum.arduino.cc/u/Paul_B)\ **Post date:** [January 11, 2021, 12:14pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/4 "2021-01-11T12:14:53Z")
Ever the "[XY Problem](http://xyproblem.info/)"! **Why** do you want a DPDT relay? Please do not say it is for reversing a motor! To reverse a motor, you use a common 2 channel relay board with SPDT relays, **not** a DPDT relay which for the same size, generally has less durable contacts. ---
**Author:** ![wvmarle](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/wvmarle/32/1013044_2.png) [@wvmarle](https://forum.arduino.cc/u/wvmarle)\ **Post date:** [January 11, 2021, 12:43pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/5 "2021-01-11T12:43:36Z")
Even so, there are far better solutions than relays for reversing a motor... ---
**Author:** ![PaulRB](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/paulrb/32/216330_2.png) [@PaulRB](https://forum.arduino.cc/u/PaulRB)\ **Post date:** [January 11, 2021, 12:49pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/6 "2021-01-11T12:49:22Z")
Assuming a valid reason for wanting dpdt, why not gang 2 channels of 4-channel spdt relay module? ---
**Author:** ![french\_guy](https://avatars.discourse-cdn.com/v4/letter/f/e5b9ba/32.png) [@french\_guy](https://forum.arduino.cc/u/french_guy)\ **Post date:** [January 13, 2021, 1:24pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/7 "2021-01-13T13:24:36Z")
> wvmarle: > Even so, there are far better solutions than relays for reversing a motor... It's not to reverse a motor....! ---
**Author:** ![french\_guy](https://avatars.discourse-cdn.com/v4/letter/f/e5b9ba/32.png) [@french\_guy](https://forum.arduino.cc/u/french_guy)\ **Post date:** [January 13, 2021, 1:32pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/8 "2021-01-13T13:32:18Z")
> Paul\_\_B: > Ever the "[XY Problem](http://xyproblem.info/)"! > > **Why** do you want a DPDT relay? > > Please do not say it is for reversing a motor! To reverse a motor, you use a common 2 channel relay board with SPDT relays, **not** a DPDT relay which for the same size, generally has less durable contacts. I do model train in DCC I need to switch the signal which is 2 wires I could do 4 SPDT (I thought about it) but if 1 relay fails, I may mix signals and not sure it's good for the DCC central or decoders in the locomotives.... ---
**Author:** ![hammy](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/hammy/32/238813_2.png) [@hammy](https://forum.arduino.cc/u/hammy)\ **Post date:** [January 13, 2021, 1:34pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/9 "2021-01-13T13:34:49Z")
I guess the next point is why opto isolated , given the relay isolates it contacts from the coil ? ---
**Author:** ![wvmarle](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/wvmarle/32/1013044_2.png) [@wvmarle](https://forum.arduino.cc/u/wvmarle)\ **Post date:** [January 13, 2021, 1:44pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/10 "2021-01-13T13:44:36Z")
I'm sure there are far smarter ways of switching a signal than by using relays, which are almost certainly the wrong tool for the job. Now if you explain more precisely what you actually want to do, maybe we can give you better suggestions. ---
**Author:** ![french\_guy](https://avatars.discourse-cdn.com/v4/letter/f/e5b9ba/32.png) [@french\_guy](https://forum.arduino.cc/u/french_guy)\ **Post date:** [January 13, 2021, 2:02pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/11 "2021-01-13T14:02:33Z")
Want to do this.... I have an arduino Nanon laying around, and will need it for an auto-reverse module So I thought I would use it as well to drive relay, depending on the state of 1 switch ("Main" or "Prog") ![DCC and relays.JPG](https://europe1.discourse-cdn.com/arduino/original/4X/b/d/b/bdb6f5bd3c6def92623b11fd6892c56b95b072fa.jpeg) ![DCC and relays.JPG](https://europe1.discourse-cdn.com/arduino/original/4X/b/d/b/bdb6f5bd3c6def92623b11fd6892c56b95b072fa.jpeg) ---
**Author:** ![CrossRoads](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/crossroads/32/214033_2.png) [@CrossRoads](https://forum.arduino.cc/u/CrossRoads)\ **Post date:** [January 13, 2021, 2:12pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/12 "2021-01-13T14:12:53Z")
Wouldn't any 4-channel SPDT relay board be capable of that? There are plenty of those around. ---
**Author:** ![french\_guy](https://avatars.discourse-cdn.com/v4/letter/f/e5b9ba/32.png) [@french\_guy](https://forum.arduino.cc/u/french_guy)\ **Post date:** [January 13, 2021, 2:23pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/13 "2021-01-13T14:23:31Z")
> CrossRoads: > Wouldn't any 4-channel SPDT relay board be capable of that? > There are plenty of those around. Probably.......can 1 ouput drive 2 relays (using one of those easy to find 4 relay boards)? ---
**Author:** ![PaulRB](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/paulrb/32/216330_2.png) [@PaulRB](https://forum.arduino.cc/u/PaulRB)\ **Post date:** [January 13, 2021, 3:18pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/14 "2021-01-13T15:18:02Z")
Yes. ---
**Author:** ![french\_guy](https://avatars.discourse-cdn.com/v4/letter/f/e5b9ba/32.png) [@french\_guy](https://forum.arduino.cc/u/french_guy)\ **Post date:** [January 13, 2021, 3:20pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/15 "2021-01-13T15:20:29Z")
> PaulRB: > Yes. Just wire 1 jumper from the output to both input, that's it? ---
**Author:** ![wildbill](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/wildbill/32/1126438_2.png) [@wildbill](https://forum.arduino.cc/u/wildbill)\ **Post date:** [January 13, 2021, 3:27pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/16 "2021-01-13T15:27:55Z")
> french\_guy: > Just wire 1 jumper from the output to both input, that's it? Yes, basically. Just check the spec on your relay board to ensure that the current required for the two optoisolators doesn't exceed the pin limit on your Arduino (40mA). ---
**Author:** ![PaulRB](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/paulrb/32/216330_2.png) [@PaulRB](https://forum.arduino.cc/u/PaulRB)\ **Post date:** [January 13, 2021, 3:32pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/17 "2021-01-13T15:32:45Z")
Yes. But what is being switched? Power for something, or just a data signal? If data, analog or digital? ---
**Author:** ![french\_guy](https://avatars.discourse-cdn.com/v4/letter/f/e5b9ba/32.png) [@french\_guy](https://forum.arduino.cc/u/french_guy)\ **Post date:** [January 13, 2021, 3:40pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/18 "2021-01-13T15:40:22Z")
it's digital signal..... ---
**Author:** ![PaulRB](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/paulrb/32/216330_2.png) [@PaulRB](https://forum.arduino.cc/u/PaulRB)\ **Post date:** [January 13, 2021, 3:44pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/19 "2021-01-13T15:44:52Z")
What voltage? ---
**Author:** ![wvmarle](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/wvmarle/32/1013044_2.png) [@wvmarle](https://forum.arduino.cc/u/wvmarle)\ **Post date:** [January 13, 2021, 3:53pm UTC](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793/20 "2021-01-13T15:53:41Z")
> wildbill: > Yes, basically. Just check the spec on your relay board to ensure that the current required for the two optoisolators doesn't exceed the pin limit on your Arduino (40mA). Make that 20 mA (40 mA is the absolute max and not to be used as design spec). > french\_guy: > it's digital signal..... The 74HC125 or 74HC126 can easily switch digital signals. [Next page](https://forum.arduino.cc/t/2-channel-relay-board-with-5v-dpdt-relay/690793.md?page=2)