Hello, I've done some research that this is probably the solution but I haven't done Arduino before.
My goal is to control 16 1.5amp(+margin)@12v DPDT
What do I need to buy from Arduino to make that happen?
Fleshing out, each dpdt switch controls a solar panel motor. So I don't need to run all of them at the same time.
1.5amp peak
Thank you!!
Enough?
You want the Arduino to control a DPDT relay ?
This is to reverse a voltage applied to what ?
What else do you anticipate the Arduino doing ?
Hello planetpeacepeacepeace
Welcome to the best Arduino forum ever. 
Post a block diagram of your project.
A picture is always worth a thousand words.
A single DPDT will give you fwd/rev but no STOP.
Two SPDT will give you fwd/rev and stop.
Tom.. 
The purpose of this is to control 16 motorized solar panel lifts (1 axis)
I haven't purchased the lifts yet.
I would like to use a GPS location to calculate the correct angle through the day for the solar panels (rather than a photometer)
The info I've gotten from the vendor is that each lift is controlled by a DPDT switch, 12v, 1.5amp peak.
And that other customers have used Arduinos
"Compatible with DPDT switch" not much more info
Thanks!
A MOSFET would be used to pick the relays.
Low current requirements might be handled by a DIP miniature relay.
That seems to tell us you want the panel to follow the sun from sunrise to sunset. Can you explain how GPS location can help with that?
Here's 1 repo I'll look at, I'm sure there's others.
Incase you are asking conceptually,
GPS and sun path calculations is essentially the same as a locations dawn/dusk data
I expect to have some local rest server that tells the Arduini which panel to lift or adjust to what angle.
There's no reason to move all the panels at the same time except to look cool. Batching position adjustments will cause a smaller combined amp draw, which I assume impacts the needed hardware.
Since a switch won't give me position (extension length) I'll have to depend on an expected time between 0 and 50' to figure out how quickly the lift adjusts the panel, assuming that it's a consistent speed, and store position (the web service will track this) for periodic adjustments.
I assume I could use distance sensors, which would give me warning of equipment degradation. But it's getting complicated.
Additionally, a gyro could be added to concepate for ground tilt.
You can hang hundreds of switches on daisy-chained input shift registers connected to MCU 4-wire SPI bus or shift port pins.
Arduino is a System that includes the IDE and choice of boards including DIY controller chip stand-alones. It is Open Source, rolling your own isn't just allowed, it is encouraged!
If you dig, the forum will help!
Why not using LDRs or other light sensing devices?
You don't have to know the time of day or your exact location on the earth.
Tom..
It doesn't seem to me you need any physical switches for what you want to do. I'd use a H-bridge for each motor instead. If you don't need to run these at the same time, you could even economize on GPIO's by using only two GPIO's to run all the H-bridges and select which H-bridge is enabled through a latching mechanism. However, since it's only 16 motors, you could also simply use an Arduino with sufficient GPIO's (Mega e.g.) or a GPIO expander.
The concept as such sounds perfectly fine, sensible and feasible to me. Yes, there are other ways, such as something involving light sensors, but frankly, we don't really expect the sun to move around the sky very erratically, so why bother. A calculation based on location + time of day will be perfect.
A red led plugged backward between an analog pin and ground, and a small program is enough light meter for the job. With 4 leds around a soda can, any shadow cast by the can can be quickly and cheaply detected.
An old wilderness trick is to put a straight stick into loose dirt so it casts no shadow and wait a few minutes. A shadow pointing east will form.
In the same way, shadow can be used to track sun movement to chosen closeness.
Are you me
I have a mostly-built control system (for a single panel though, and with much higher motor current needs) that does this (+more).
Basically, takes GPS input and calculates optimal panel angle relative to horizontal based on time of year and moves the panel to that position with feedback from an inclinometer. Are you moving all the panels to the same position? I don't see any mention of how you're going to measure the panel angle so you know where to stop.
My system has more features than you mention, but if you'd like to get some design share, send me a PM. The first thing I'd mention is that I avoided relays. I considered them, but I also wanted the option of having speed control of the panels, which required a PWM output, so I opted for high-current H-bridges instead.
I think I have a video somewhere if I can dig it up.
I cannot figure out how to DM you! Haha, I've felt that "are you me" feeling before this year too.
It sounds like H bridges is the way to go, or maxing out a mega gpio.
As for determining current position I think I mentioned that I was thinking of doing a timer and keeping track that way, which probably won't be very accurate. Maybe I even have to max the tilt every time and then lower them so it's a more consistent precise adjustment. (10sec to lower panels, 50', 5'/sec for example).
How are you measuring position? I was thinking alternatively that distance sensors are pretty cheap but I'm not sure how to mount it solidly. And it adds complexity.
What features have you built in?
This is actually for a skoolie conversion, I'm buying the bus in 12 hours!!! Yeeee
