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I am working on home vertical growing project.

INTRO

I am using:

Below is my wiring diagram (it is not the nicest, but I don't know what programs are you using for better drawings). There is not shown, but those "INx" signals from relay module are connected to arduino digital pins. In total there will be 6 relay modules.

Schematics

So the relay model datasheet says each channel needs 15-20mA that is 60-80mA per module. relay_characteristics

And L7805CV can deliver from 5mA to 1A. L7805CV electrical characteristics

PROBLEM

At first I was supplying 3 modules with only 1 L7805CV, but when I tried controlling modules only one relay clicked, but the leds were lit up for all of them but they were dimed. At this point there was no Arduino connected I was using only one wire and connecting it to 5V or GND, controlling one relay at a time.

So I thought it was problem with power supplying, and added one L7805CV for each relay module. And now sometimes they "click", sometimes they don't and sometimes they are "clicking" like crazy while control signal is not changing. And sometimes there are some wired buzzing sounds.

Are there any suggestions?

Thanks in advance for all the answers.

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    \$\begingroup\$ The link for the power supply does not work. Is the jumper on the relay board removed or connected? Either way the relays should not be randomly clicking, no matter what. \$\endgroup\$
    – Justme
    Nov 5, 2021 at 8:47
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    \$\begingroup\$ @Justme Jumper is removed. \$\endgroup\$
    – ves_el
    Nov 5, 2021 at 10:53
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    \$\begingroup\$ @tlfong01 I will check your answer. Is L7805 not good because of the voltage drop on it? I have a plan to change it in the future for some other switching regulator, probably L2596 as you suggested. I just had some L7805 laying around so I can start testing other parts of the system. \$\endgroup\$
    – ves_el
    Nov 5, 2021 at 10:57
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    \$\begingroup\$ Did you applied heatsink for 7805? It has internal thermal protection. From 12V to 5V, 1A , 7W should be dissipated. Without heatsink it can dissipate 0.35W or less, depends on environment. \$\endgroup\$
    – user263983
    Nov 5, 2021 at 12:54
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    \$\begingroup\$ @user263983 Thanks for pointing that out. There are no heatsinks applied at the moment. This is just for quick testing purposes and I am going to change L7805 for a switching power supply as was sudgested by tlfong01. \$\endgroup\$
    – ves_el
    Nov 5, 2021 at 14:28

1 Answer 1

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You haven't drawn any capacitors on your diagram. A 7805 needs them on the input and output, as shown in the data sheet. Without them, the output of the regulator can be unstable.

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    \$\begingroup\$ Thanks for the heads up, I will add them and report how it went. \$\endgroup\$
    – ves_el
    Nov 5, 2021 at 10:59
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    \$\begingroup\$ I added capacitors to input and output of L7805 and now relays are acting normal. Regulator unstabiliti explains why relays were clicking randomly. \$\endgroup\$
    – ves_el
    Nov 5, 2021 at 14:24
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    \$\begingroup\$ So that is he issue. 50 mA you can get without overheating. Also relay coil 5V you may feed from 12V with resistor in series. \$\endgroup\$
    – user263983
    Nov 5, 2021 at 16:59

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