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Hello, I am a beginner at electronics. I have two AC to DC converters ((3),(5) in image). The converter with the number 3 is connected parallel with my room's light bulb. It converts 220v AC to 12V DC 1.2 A. The converter number 5 is a small 220v AC to 12v DC 450mA converter. Devices 4 and 6 are arduinos. Number 7 is a switch. and number 1 electricity mains. The problem is that when I attach the number 5 on the circuit then it draws all the current and number 3 does not light up. Why?

Update: I have an arduino inside my light switch which takes values from a trimmer and send it to a Central Arduino which send them to the Arduino which is parallel connected to the light bulb and dimms the light using a phase control module.

when I disconnect the inverter number 5 the circuit works perfectly. When I connect it back the LED on the converter number 5 turns constantly on but the LED on the converter number 3 turns on for some milliseconds and fade out. With a result the arduino parallel connected to the light bulb to not work

Update 2: This is the complete circuit. I use nrf24l01 modules to communicate between arduinos. The dimmer is a circuit that detects the zero-crossing and uses a triac to control current. There is a tutorial on Instructables. Update number 2

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  • \$\begingroup\$ So why does the lower Arduino have to be in the light switch. Why can't it be powered from a socket since all communication is wireless? \$\endgroup\$
    – Transistor
    Nov 16, 2015 at 2:38
  • \$\begingroup\$ Because I want to replace this light switch with another made by me (the lower arduino) which will have a trimmer and a button controlling various staff. \$\endgroup\$
    – Christos Mitsis
    Nov 16, 2015 at 2:46
  • \$\begingroup\$ Why not put back the regular light switch and use a small battery-powered wireless or infra-red transmitter to send the commands to the Arduino light controller. Your 'trimmer' (potentiometer / pot) and button could be replaced by a small unit with 'up', 'down' and 'enter' button. It will only transmit when button is pressed so battery will last a long time. Much safer too. I'm sure you'll find a suitable transmitter / receiver on eBay. \$\endgroup\$
    – Transistor
    Nov 16, 2015 at 20:48
  • \$\begingroup\$ Well, I think that I will conclude in this solution. Thank you. \$\endgroup\$
    – Christos Mitsis
    Nov 17, 2015 at 13:52

1 Answer 1

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@Christos, 5 requires a live and neutral connection from the mains.

With your poor understanding of electrical circuits at the moment you should not be doing any mains wiring. Stick to low voltages. Use plug-in power supplies and only plug them into sockets - not the lighting circuits.

[Edit after Christos' update.] There are a few problems but let's make an easy example. Let's say you have a 100 W lamp and a 5 W Arduino power supply and let's make the maths easy by saying the mains voltage is about 200 V. The bulb would draw 100W / 200V = 0.5 A on full mains voltage. The PSU would draw 5W / 200V = 0.025 A. Since they're in series the PSU will limit the current and the lamp may glow a little but certainly won't light up.

Your circuit doesn't show a dimmer element in series with the light bulb so it's hard to know how you're hoping to control it.

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  • \$\begingroup\$ I need to supply with current an arduino inside my light switch. There is no other way to supply it. Is it so difficult to make both converters work? \$\endgroup\$
    – Christos Mitsis
    Nov 16, 2015 at 0:10
  • \$\begingroup\$ Yes. Both converters need full mains voltage. Connecting (5) in series with the light bulb is not a good idea. Edit your original question and tell us what you're trying to achieve and someone will give you a safe way to do it. \$\endgroup\$
    – Transistor
    Nov 16, 2015 at 0:14
  • \$\begingroup\$ I will post an update in about an hour with a new circuit showing all of the modules attached to the circuit and arduinos. I hope to find a solution \$\endgroup\$
    – Christos Mitsis
    Nov 16, 2015 at 1:48
  • \$\begingroup\$ +1 for writing "With your poor understanding of electrical circuits at the moment you should not be doing any mains wiring. Stick to low voltages." How do we know your understanding is insuffcient ? One look at your schematic says enough. Look at other people's schematics and learn from those. \$\endgroup\$
    – Bimpelrekkie
    Nov 16, 2015 at 10:37
  • \$\begingroup\$ At this moment, even my understanding isn't enough, I need to have an answer. If you could answer me, it would be appreciated. Even \$\endgroup\$
    – Christos Mitsis
    Nov 16, 2015 at 11:18

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