# Solar charger & timer

#### 3876764

Joined Jul 10, 2020
9
Hi
I need help building the electronics for a home project. Essentially I am trying to:
1. Charge a battery with a solar panel
2. Activate a 12solenoid valve controlling pressurized water with a push button
3. Have the solenoid close after an adjustable time delay

I was able to find solar charging and time delay circuits and got it to work initially except for the transformer I was using did not have enough power engage the solenoid under full water pressure.

Is anyone familiar with these types of circuits so I can figure this out?

#### KeithWalker

Joined Jul 10, 2017
1,919
I can probably help you but I will need to know more about what you are using. A documented diagram would be a great help.
Regards,
Keith

#### 3876764

Joined Jul 10, 2020
9
Great thank you Keith, ok let me try to put that together today. I will say the solar charger and timer or parts that I purchased via eBay. I have a mechanical engineering background so have limited knowledge on electrical circuits.

#### Dodgydave

Joined Jun 22, 2012
10,050
What voltage are you using, a smps would be better?

#### 3876764

Joined Jul 10, 2020
9
Here is a diagram. I am getting seven or eight ohms on the 1/4” solenoid valve. The issue with my current set up is the solenoid was not pulling in under water pressure probably due to the fact the transformer wasn’t supplying enough current. Therefore I think I need to add a capacitor or somehow get rid of the transformer by putting two 6v batteries in series for 12v maybe?

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#### KeithWalker

Joined Jul 10, 2017
1,919
The circuit looks good but to assess the operation of your setup, I need the following information:
What exactly is the "transformer"? I am assuming that it is a 6VDC/12VDC boost converter. What current can it supply?
What is the capacity and type of the 6 volt battery?
What gauge of wire are you using between the battery and converter and between the converter, relay contacts and solenoid valve and how long are the wires?
What is the contact rating of the relay that energizes the solenoid valve?
Regards,
Keith

#### 3876764

Joined Jul 10, 2020
9
Transformer is a DC 6V To DC 12V 1A Step-Up Converter.
Current battery is a lead acid 6v 4.5Ah but I would like to go smaller possibly lithium battery in the future.
I believe the wire that I have now is 16 or 18 gauge going about 2 feet.
I Purchased an automotive relay for the solenoid because I was worried that the time delay circuit would not carry the amperage, it’s rated at 40A. Maybe I should find a smaller relay too.

#### 3876764

Joined Jul 10, 2020
9
I believe the solenoid could be pulling close to 1.4A and the converter is just 1A. I just ordered a 1/8” valve that is rated at about .5A so that would help too I bet.

#### KeithWalker

Joined Jul 10, 2017
1,919
You have just diagnosed your problem. If the solenoid measures 7 or 8 ohms, it will draw 1.5 to 1.7 amps from a 12 volt supply. The converter must be going into overload protection mode because it can not supply that much current.
The wiring is fine and the auto relay should not be a problem unless its coil draws a lot of current.
A 0.5 amp solenoid or a larger converter will solve your problem.
Regards,
Keith

#### Dodgydave

Joined Jun 22, 2012
10,050
Then use a 12V battery and ditch the DC to DC transformer.

#### 3876764

Joined Jul 10, 2020
9
Then use a 12V battery and ditch the DC to DC transformer.
Hi I was having trouble locating a mini or compact 12v solar charging controller. Trying to build something in a small package.

#### 3876764

Joined Jul 10, 2020
9
You have just diagnosed your problem. If the solenoid measures 7 or 8 ohms, it will draw 1.5 to 1.7 amps from a 12 volt supply. The converter must be going into overload protection mode because it can not supply that much current.
The wiring is fine and the auto relay should not be a problem unless its coil draws a lot of current.
A 0.5 amp solenoid or a larger converter will solve your problem.
Regards,
Keith
Thanks Keith. One other thing will the nature of a 6v-12v converter always be sapping energy from the battery? Thinking I may need to try and move this to the switched side of the circuit.

#### 3876764

Joined Jul 10, 2020
9
Thanks Keith. One other thing will the nature of a 6v-12v converter always be sapping energy from the battery? Thinking I may need to try and move this to the switched side of the circuit.

#### KeithWalker

Joined Jul 10, 2017
1,919
The 6 to 12 volt converter will draw a residual current when nothing is connected to its output but it is probably very small. The only way to tell how much is to measure it or find a spec sheet for that one which may be difficult.
Regards,
Keith