Debugging a project, power related

Hi I’m building a project around the seeeduino stalker v2.0, and I’m having trouble getting it to work.

The project is a pretty simple 6 LED, 2 photoresistor, 2 photodiode setup that alternates which LEDs are on while reading each input in turn and writing to the sd card.

Everything works while it is plugged in via USB (FTDI cable), but when I switch to battery (12V 2400mAh Nicad through a L7805CV regulator to the solar input terminal), the program continually resets at or just after reading the sd card.

I’ve put an ammeter in and get about 24mA draw during the startup.

The red CH led has a very faint flicker to it when on battery power that is not present on USB.

I read 5V at the output of the 7805 on battery power, but 0V at the USB5V output of the arduino. When on USB power I read 5V at the USB5V.

I read 2.5V on my +5V rail of my project board on battery power, but 5V on USB power.

Also having no luck with the RTC, but that’s a separate issue.

Any help or thoughts is much appreciated.

Why do you power it through solar panel connector not the battery connector?

Anyway, you won’t get 5V, when not using USB. It’s weird and different from regular Arduinos, but it is so. Stalker has 5V only when on USB and 3.3V, if you use battery or solar panel as power source.

(It took some time for me to realize this, but now I use 3.3V from the start of a new project, ignoring the 5V power pin, since it won’t be available later, when I switch from USB to battery.)

My understanding was that external power should go to the solar input, as the battery has all the charging circuit. Figuring out how to power this was a lot of reading around. A manual would have been nice, the wiki is lacking on details. I can’t find where I was told to power via solar, might have been a forum post.

I suppose that there is no chance that the seeduino would try and charge my nicad if I leave the solar input disconnected?

I’ve tried putting a wire from my regulated 5V to the FTDI pins to give “USB power” while on battery.

I need 5V in the circuit to drive a 4V white LED.

Stalker won’t try to charge your battery, if it has no other power source. :slight_smile:

As for 4V LED, it’s tricky. I’d suggest to use another LED, that has acceptable requirements, or use a separate power supply for LED and connect it to your Stalker, using a TIP120 transistor, for example – … nd-tip120/. It’s easy and requires no change in your code.