My electronics knowledge is extremely basic, but i have started playing around with Arduino Uno to which i send commands from a C# program. For a next project, i would like to extend my set up in order to use my computer to control a smoke machine similar to the one bellow: 400W fogger, powered by 220~250V 50-60Hz

It is a 400W fogger, powered by 220~250V at 50-60Hz. You basically turn it on, and then use the (plugged-in) remote in order to blow smoke (or not). Ideally, i would like to replace the physical switch on the remote and use an Arduino to communicate with the fogger and trigger the smoke blow. I found similar posts (e.g. Replacing a mechnical switch with a digital one), but they seem rather complicated compared to the set up i have at hand. I opened the remote and here is a Fritzing sketchup of its inside: enter image description here

I saw some posts mentioning the use of relays in order to control the remote state (BLOW or NO BLOW), and i do have a small relay at hand that was shipped together with my arduino kit (1 Channel 5V Relay Module). To my understanding, you have to be careful when using relays since without proper knowledge you can damage your hardware or even harm yourself pretty badly.

I guess i am looking for a few tips or hints from other people (since i am quite a beginner and have nobody around me i can ask for advice) on whether or not using a relay would indeed be a good option. Any other comment or information is of course more than welcomed.

Thanks in advance

  • \$\begingroup\$ Please add details about the relay module - are there any markings on the relay itself? This should be relatively simple to achieve, but since the push switch appears to be switching mains voltage (albeit at very low current) we need to make sure that the relay is appropriately rated. Also, you will be working with mains - at low current - but certain precautions should be taken, which a good answer will cover. \$\endgroup\$ – stefandz Sep 11 '15 at 9:02
  • \$\begingroup\$ The relay i am using is the one described in the following link: tkkrlab.nl/wiki/Arduino_KY-019_5V_relay_module .The markings are: 10A 250VAC, 10A 125VAC, 10A 30VDC, 10A 28VDC. (Sorry for the poor formatting) \$\endgroup\$ – PastonZZZ Sep 11 '15 at 9:27
  • \$\begingroup\$ If it is of any help, i attempted to design a circuit using the relay i mentioned in my former post. Since i cannot find a way to upload another image on my original post (limited to 2), please find the following imgur link: i.imgur.com/SnwuMjK.png \$\endgroup\$ – PastonZZZ Sep 11 '15 at 9:43
  • \$\begingroup\$ Your two circuits (your designed one and the one you link) look different to me. How many switch positions are there? And how many connections on the switch? Which LEDs light up and when? This will help us to help you with the design. Also, did you already build and test the linked circuit, or was it theoretical? \$\endgroup\$ – stefandz Sep 11 '15 at 10:05
  • \$\begingroup\$ The switch from the original set up provided by the manufacturer has two positions, and two connections. When the machine is at rest (no smoke blowing), the red LED is on. Then if you press the switch once, smoke comes out, the green LED is on, and the red LED is off. If you press the switch once more you go back to "rest state". The linked circuit is theoretical, i haven't tried to build it yet. \$\endgroup\$ – PastonZZZ Sep 11 '15 at 10:11

From the information you have given in your comments, your original circuit should be fine. I am including it below for the benefit of others.

Switch replacement circuit

A few safety notes, since it does look like this switch is switching mains.

  1. Always unplug the unit before working on it. Don't just switch it off at the wall - at some point you will forget and hurt yourself. If I am working on stuff that really scares me, I have an extension lead with a light plugged into it, and then plug the device I am working on into the extension lead. That way, if I only ever unplug and plug in the extension lead I have, there is a light on when the unit is energised. I used to work on x-ray power supplies, so it was a bit more critical to me then :)

  2. Before touching any wires, use a multimeter to check for any residual voltage from electrolytic capacitors that remain charged or circuits that they are powering. This will normally be DC, but you might as well check on both DC and AC settings. The likelihood of there being any danger with this particular unit is very low, but learning good practise now will always be useful later.

  3. Be neat and tidy with your wiring. If you nick insulation, cut the wire back and restrip. Don't have lots of exposed copper hanging out of screw terminals - strip back just the amount you need. Be sure to give all screw terminals a reasonable "tug test" to check that the wire is secure.

  4. Be neat and tidy with your circuit boards! Think about where your relay module is going to go, make sure it is securely affixed in the final build. Make sure that the bottom side of the board isn't going to contact any other conductive material.

  • \$\begingroup\$ Thank you very much, i really appreciate your help and comments! \$\endgroup\$ – PastonZZZ Sep 11 '15 at 10:29

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