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Spooky stuff happening on a DIY power breakdown protection

Spooky stuff happening on a DIY power breakdown protection

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  #1  
Old 08-23-16, 09:51 AM
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Spooky stuff happening on a DIY power breakdown protection

Fist of all, I'm not English native so if something is not clear, post back.

I'm currently working on a DIY fish tank control center. It will be a arduino based system that basically control different power sources for 5 and 12 vdc (ledstrips and relays), some sensors (temp, ph, low level water, power source temp, voltages and currents) and some 110vac relays for heaters and emergency pumps. To make it short, the system will run automatic dataloging in an sd card and automatic water changes + light timers.

I have some knowledge in electronic but I have not done any for many... many years.

I had 2 big 12vdc batteries at home doing nothing. I wanted my system to be breakdown protected so I set up a circuit with diodes and a main relay (controlled by my AC -12VDC source) that switches the anode from the battery to a charger when activated, and to my circuits when AC unpluged.

I realized that the delay for the relay switching when turning off AC was too long for my arduino system to keep going. I took some capacitors, put them in parallel and made a 12VDC accumulator. (See picture, the only difference is that I think in the real circuit I experiment with, the main switch is on neutral, not live. I didn't draw the AC ground but everything is pluged)
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The system is working fine.
=======================
HERE FOR THE SPOOKY PART.
When running on battery (AC unpluged, main relay deactivated), the relay switches for a millisecond. Not long enough to make my arduino reset, but long enough to make my LCDs dimm low.
SPOOKYER
The other day, I walked by my project table. The circuit was off for 4 hours at least. I saw my lcd backlight turn on for a millisec, like a strobe. the battery is unpluged and the main switch is off.


The hardware part of my project is very advanced now but I am running into some spooky stuff happening with my 12VDC source. Can somebody show me a way to prevent this leakage or maybe a better way to create a breakdown prevention system.

Thanks all for your time!
 
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  #2  
Old 08-23-16, 05:46 PM
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When you say the relay switches for a millisecond, do you mean the relay that switches the battery from the charger to the circuit?

Assuming that's the relay you mean, it would seem enough voltage is being applied to it to cause it to briefly switch. The only place it can be coming from is what you have marked "12 volt without battery" since you have diodes between the capacitor bank and the 12volt with battery section.

I suggest you add a diode in series with the 12 volt without battery line and see if that problem goes away. Without knowing what is connected to that line I can't speculate what might be sourcing voltage there.....
 
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Old 08-23-16, 10:03 PM
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Welcome to the forums.

Instead of switching from DC supply to battery with a relay for the processor....... the processor should always be powered. Hot standby. You could eliminate all those big caps.

Use the relay to switch the power to all the external devices.

Use a circuit like this to power just the processor.

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Old 08-24-16, 07:48 PM
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Thanks for your help

I already tried the diode on the 12vdc nobat out. Better than that, nothing is plugged there.

For the Relay, I need the relay to switch the battery from circuit to charger when DC is present.

Is it possible, since my project is garage style with wires all over it, that 12vdc, 5vdc wires + can induce current randomly in circuit?
 
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Old 08-29-16, 06:44 AM
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I'm using my circuit for a week now with the battery unpluged, the relay stays on without interruption, so I wouldn't think it would be magnetic parasites.
 
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Old 09-09-16, 07:55 AM
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Turned out that my AC to 12vdc supply is defect and send a pulse every 5-10 minutes when only connected to Live wire...
 
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