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I am doing a water plant project. I need to control multiple solenoid valves with my micro controller circuit using relays. When I connect more than 4 solenoid valves (12 V) with a 15 V adapter it will cause a voltage drop and the solenoid valves are not working.

Questions:

  1. Why does this happen and how can I fix this problem?
  2. How can I connect multiple solenoid valves (ex:64 solenoid valve) with a micro controller using relays?
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    \$\begingroup\$ How much current can your 15 volt adapter provide? How much current do your individual solenoids take? Do the math. \$\endgroup\$ – Andy aka Oct 9 '18 at 11:33
  • \$\begingroup\$ my adapter is 15v 1amp adapter, it works for 4 solenoid valve. but it not working on more than 4 valve \$\endgroup\$ – Natesh Oct 9 '18 at 11:59
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    \$\begingroup\$ And............... \$\endgroup\$ – Andy aka Oct 9 '18 at 12:04
  • \$\begingroup\$ each solenoid valve takes 12v 500mA current, \$\endgroup\$ – Natesh Oct 9 '18 at 12:09
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    \$\begingroup\$ You figure out the maximum number that will be on simultaneously, total the required current, multiply by a safety factor and buy a power supply that meets or exceeds that specification. \$\endgroup\$ – Transistor Oct 9 '18 at 12:53
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As answered in the comments, your power supply is not sufficiently powerful to supply the needed current. Current required is cumulative for device's in parallel, so you must add the needed current numbers together.

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Most of the time the voltage drop is caused by the excessive current drawn , note that many wall adapter are not regulated and their output voltage vary as current drawn by the circuit increase ( this depends on the topology ) .

For your question #2 , yes you can connect as much solenoids as you like using a micro-controller , even if each one requires separate control , make sure you have sufficient pins in the micro (I/O) if that is not what you meant and you want all 64 solenoids to work at the same time that is also possible .

Make sure to do the following : 1- power supply output current > total solenoid current 2- Relay rated current > each solenoid current 3- micro-controller pin is buffered to by transistors or gates in order to supply current to the relays coils.

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