Raspberry Pi Forums

We're trying to use our Raspi for two purposes, one, to digitally record temps every 15 minutes and two, drive a small motor. The motor is very slow and is 12 v - 1 Amp. Since it's gear motor, we want to use it to turn a parabolic reflector for solar hot water heating...

more info here:
http://www.appropedia.org/Parabolic_Sol ... ter_Heater

Another question... on the newer Raspis, i noticed that they have more on-board memory, up to a gigabite it think. Is there any way of NOT using a SD card to run this?

Have a great afternoon!

You can't directly run that motor off the Pi, but you could control it with an appropriate relay or transistor controlled by the Pi and an external 12V power supply of some kind.

Thanks, moti555, for replying! That's what i suspected with the motor, but if i can use the Raspi to replace the sun tracker board i have to buy at this point that should more or less make up for the extra board/transistor/relay i might need to invest in.

Since we're already using a sun tracker, we already have a 12v regulated power supply. i'm just tired of trying to get the sun tracker to work/aim correctly and may just go with some sort of program on the Raspi and a connection to the net for the time and day (which will also come in handy to upload the data from the temperature probe).

Again, thanks for replying and have a great afternoon!

frazelle09 wrote: Another question... on the newer Raspis, i noticed that they have more on-board memory, up to a gigabite [sic] it think. Is there any way of NOT using a SD card to run this?

All the code for the GPU, Videocore and ARM processor is loaded from the SDCard. You can't avoid that. You can move the root filesystem to a USB device. But the bottom line is you need an SDCard.

12V 1A .. a standard (inexpensive) L298N module can drive that easily.

Dougie - geez it's like raining answers here! - lol

Thanks for the great explanation. It's just that a giga seemed an awful lot - maybe i should see how much the OS really occupies.

Anyway, thanks for replying and have a super afternoon!

mikronauts - thanks for posting. i'll have to check out the link. Maybe i can use the four leds from the sun seeker we have and put together a circuit that can use the Raspi to better detect the sun's position.

Have a wonderful afternoon!

frazelle09 wrote:Dougie - geez it's like raining answers here! - lol

Thanks for the great explanation. It's just that a giga seemed an awful lot - maybe i should see how much the OS really occupies.

Anyway, thanks for replying and have a super afternoon!

The 1 gig memory is all Volatile memory, it doesn't retain information when the Pi is powered down, this is why you need a SD card, to hold all of the necessary code for running the Pi while the power is off.

Non-Volatile memory is needed to contain the code that the Pi needs to start up, The Pi is set up so that it will always check the SD card for this code when it starts up, if the code isn't there then the Pi will not work.

There is a way to reduce the required size of the SD card by minimizing the amount of information on it and adding a redirect to an alternative storage location (generally a USB memory stick or hard drive) which contains the rest of the OS code.

But a SD card is absolutely required to tell the Pi where to look. (and as a 8GB SD card costs £4 you might as well have one that can contain the entire OS unless you have a good reason not to).