Using a solar charger for Outdoor Arduino Project

Thread Starter

bobinbd

Joined May 28, 2016
23
I am working on a simple Arduino nano device that will act as a deer alarm when deer are in the yard. Essentially it has a motion sensor an ldr and at the moment a buzzer that plays a melody but I hope to change that to an sd card with cougar sounds on it and a small speaker. There are also two leds that might seem like cougar eyes in the dark.
The ldr is programmed to avoid the buzzer in daylight.
I want to power this with a cheap solar charger (8000 mah).
Conceptually, these seems sound. The buzzer works when plugged into a simple usb charger, but it isn't very portable that way.

Now, the solar charger acts kind of weird. I had the nano down to using less than 10ma when it senses no motion and 46ma when the buzzer is sounder. However, the solar charger cycles on and off after about 10 seconds if there is less that about 60ma of current going out. I have tested this with a bank of leds and found if the current is at 67 ma or more, they stay on indefinitely, but if I take one led off (down to 55ma) then the charger cycles off and then on again. So rather than having this work with low power, I have to make sure my circuit consumes at least 60ma at all times. I have another 12000 mah charger and I haven't found the spot where it just cycles off yet (more than 87 ma!)

I am hoping that during the day the charger will charge up and have enough power to drive the Arduino at night. But it needs to stay on at least during the night time, and the cycling on and off makes it pretty useless.

So my question is, have other people tried using these solar chargers (really made for phone chargers) as the power source with outdoor Arduino projects and if so, what have your experiences been and do you have any useful observations to make on this kind of setup?

They don't actually have to be used just for outdoor projects. Even portable projects. They seem to make a good power source at low cost!
 

wayneh

Joined Sep 9, 2010
16,128
I don’t understand what you mean by the charger cycling. Why do you even care what the charger is doing, as long as it works? Your device runs off the battery and should be independent of what the charger is doing.
 

Thread Starter

bobinbd

Joined May 28, 2016
23
I don’t understand what you mean by the charger cycling. Why do you even care what the charger is doing, as long as it works? Your device runs off the battery and should be independent of what the charger is doing.
Sorry I wasn't clear enough.

The charger cycles on and off. Stays on for about 10 secs and then turns off for about 1 second and then goes on again etc. So if I wanted to have flashing leds, this would be fine, but the nano barely gets started into it's program and then it is off and has to start over again. It is only if I am drawing over 60ma of current will it stay on without cycling on and off.
 

ericgibbs

Joined Jan 29, 2010
9,105
hi bob,
I assume that the cycling solar charger does actually charge your battery during the day.?
So if the battery is say fully charged during the daylight hours by the charger, it does not matter when it is dark if the solar charger is 'working' or not, or am I missing something.?
Eric
 

blocco a spirale

Joined Jun 18, 2008
1,546
I think by "solar charger" he is referring to a powerbank with a solar panel attached. Powerbanks usually switch off if there is insufficient load connected to them.
 

ericgibbs

Joined Jan 29, 2010
9,105
hi blocco,
You could be correct.?
The OP mentions night time working of the project, so I have assumed that the solar charger is charging a suitable battery for the night time.
Perhaps he can confirm.?
E
 

Thread Starter

bobinbd

Joined May 28, 2016
23
solarcharger.PNG
hi blocco,
You could be correct.?
The OP mentions night time working of the project, so I have assumed that the solar charger is charging a suitable battery for the night time.
Perhaps he can confirm.?
E
Attached is a picture of the solar charger. Here it is used to charge/power a phone. I want to use it to power an Arduino nano, but yes it does seem to power off (momentarily) if the load is not sufficient. For this unit it seems to be about 60ma. My nano draws only 43ma when the buzzer is going and the led's are on so I guess I have to add some extra load! The load will actually be minimal during the day (not really required) but active at night. I may just have to go turn the power bank on at night. I just don't want to have to connect the nano to house current when my project is out in the yard (trying to scare the deer away from eating the flowers).
 

Thread Starter

bobinbd

Joined May 28, 2016
23
What will power the project during the night.? There must be a battery if you do not want to use mains.
Yes, that solar charger has a LIPO battery installed. Can power 8000maH, so if I were to draw 100ma, it should last 80 hrs, but it should recharge during the day so hopefully it will have indefinite power (charge during daylight, discharge during night).

The nice thing about the solar charger is that it was like $11, has the photovoltaic panel, and circuitry to output 5volts (or is USB 5.5v?) anyway just right for the nano. But I guess not if you have the nano running at low power. It has a nice waterproof case and the built in battery. It seems perfect for portable type Arduino projects. But I guess you have to make sure you draw lots of power when using it!
 
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