New Project, Stepper Motor for outdoor use

I am starting a new project and am going to use one of my Arduinos for it. Basically I am going to make a solar tracker. I am going to get the 45w solar kit from Harbor Freight ( http://www.harborfreight.com/45-watt-solar-panel-kit-68751-8527.html ) and a couple of 65ah batteries. The purpose of this is to supply 12v dc power to a gate opener that is WAY too far away from a power source. I have a tendency to over build but I want to make sure this thing always has a charge on the batteries.

I have most of the base built to house the electronics, controllers, batteries and to hold the solar panels about 12 feet off the ground. This will hopefully keep people from messing with it. But like I mentioned the solar tracker part his going to be exposed to the elements, sun, dirt, dust, ice, snow, rain etc. I want to make sure that I get steppers and/or servo motors that are going to last for this. Based on the shipping weight of the solar kit I think that I want to go with something like a nema 34 possibly a nema 23 but what do I get to ensure they can handle the elements?

I read something on IP65 but man those are expensive.

DO NOT, repeat DO NOT consider using a stepper motor for moving a solar panel. Stepper motors are extremely inefficient and will use all the power the solar panel can provide, and more. Stepper motors need their full current even when stationary.

If you need a powerful drive use a DC motor with a worm gear. The worm gear will allow the panel to hold position even when the motor power is switched off. A used car screen wiper motor may be suitable.

...R

Instead of steppers, have you considered using something like windshield wiper motors? They can be had fairly cheap from a junkyard or pick-ur-part place, they are generally worm driven (so no backdriving possible - so you don't have to keep re-adjusting the position because of wind or such - which I hope you were designing in for a stepper solution), and are fairly robust in the elements.

Even so - for either solution - you would probably want to house the motor in some kind of water/dust-proof enclosure, and only expose the shaft to the elements.

Another solution (so far untested by myself - though I am planning on playing around with the concept later this summer maybe) - drop the tracking entirely (yeah, I know, not as fun).

Find out what the average altitude angle for your latitude is to face the sun; this won't be the optimum angle for a panel, but really it will be close enough for most purposes throughout the year. Then all you need to deal with is the azimuth angle to track the sun (note, this could be done for a single-axis motor-controlled tracker as well).

What you do (again - this is untested) - get the lenticular screen from an old big-screen projection TV; people are throwing them away all the time, and usually the front lens is fine - maybe a few scratches on the lenticular lens (note - you'll also get a huge fresnel lens in the bargain - great for those times when you need to melt rocks or something of that nature!).

Place the lenticular lens smooth-side down on the solar panel, with the ridges "vertical" to the ground-plane. The "ridged" side is actually a series of cylindrical convex lenses designed to take the light from the projector, and spread it so that the image on the TV can be seen from a wide angle (150-170 degrees or so). Since you would be using it in "reverse" - it should be able to collect the light over that azimuth angle range, and direct it "straight" to the solar cells.

At least - that's the idea - like I said, I haven't tried it, but over the past couple of months I have managed to salvage 3 large fresnel and lenticular lenses from big-screen projection TVs that people were throwing away (bulk trash pickup in my area). The lenses are fairly easy to remove; I can strip one off a TV inside of 10 minutes. You'll also find a huge silver first-surface mirror inside as well (laser experimentation parts).

It's funny - most of the time when I see these TVs by the side of the road, people have stripped them of the projector, but leave the lens alone. Personally, I prefer the optical path components. Sometimes there are some nice mag-shielded speakers to be had, and if the unit was a triple CRT projector, and you are willing to take the time to carefully remove them, three large (4-6" diameter) projection lenses can be had too (note that some of these units used a coupling fluid between the CRT and the lens for heat removal - the fluid is something like mineral oil or such, and I am not sure how bad it is for the environment - or your skin/hands/body/health).

Good luck!

Oh - I forgot to mention - on the motors (if you choose to go that route) - you will want to have some kind of positional feedback to track the angle; generally a potentiometer is the lowest cost solution. It is also possible to modify a standard RC servo to control a larger gear motor to effectively create a low-cost but large servo motor. Google for "diy big servo" and variants for ideas, etc.

Also - while using a stepper motor on it's own will require it to constantly need current to keep the panel stationary, nothing prevents you from using such a motor with a worm drive, or as part of a linear actuator system to prevent backdriving of the motor.

In fact - a pair of linear actuators (whether powered by steppers or DC gear motors) could be DIY'd fairly easily, and because of the design you will likely need an enclosure to house the motor anyhow for protection from the elements.

The Harbor Freight panels are a poor deal. You can buy a high quality 100 watt Grape Solar panel from Costco for $149.

http://www.costco.com/Grape-Solar-100-Watt-Polycrystalline-PV-Solar-Panel.product.100054656.html

Hi

Did you consider to use a polar mount form a satellite dish ?

I saw couple of commercial panel ( big ones ) build with polar mount as sun tracking system.

Used one could be cheap. Most of the motors, ( 24v-36v dc, can be from 1.5 to 5amp, actuator ) and have build in sensor, encoders, and limiter position with internal switch. . Outside use only. ( all protected from the elements ) Far form the ground, as you wish.

Most motors are not designed to cope with outdoors at all. A fully encosed drive system would be ideal. Even motors that look pretty sealed will just rust - the laminations, bearings, shaft, they will all rust if damp. You pay extra for fully sealed motors (for instance stainless steel shaft is a requirement, laminations have to be enclosed in an outer jacket, proper shaft seals...).

Here ya go. Weather resistant, powerful, inexpensive, readily available, easy to mount, and worm gear driven. An automotive window regulator. - Scotty

|500x375

Automotive motors are likely to be galvanized too, since condensation is rife in vehicles.

WOW thank you for all of the feedback. I guess stepper motors are out. I got some for free from a friend and was thinking about using them but if they need power all the time that is pretty much out. Obviously I am new to steppers. I considered a linear actuator for one of the axis. But since I have a car my brother in law blew a hole in the block on and I am taking apart I can use window motors or wiper motors. I forgot about the wiper motors in my list of parts I want to keep so thank you for that as well. These will be much cheaper to work with anyway since they are free and well I dont need to buy any high amp stepper controllers.

jremington: The Harbor Freight panels are a poor deal. You can buy a high quality 100 watt Grape Solar panel from Costco for $149.

http://www.costco.com/Grape-Solar-100-Watt-Polycrystalline-PV-Solar-Panel.product.100054656.html

Sweet noted and will buy, I was hesitant on the HF panels anyway, because well its HF.

arssant: Did you consider to use a polar mount form a satellite dish ?

The idea here is to build it from scratch. Why because I want to learn more and it gives me something to mess around with.

cr0sh: Another solution (so far untested by myself - though I am planning on playing around with the concept later this summer maybe) - drop the tracking entirely (yeah, I know, not as fun).

Yeah I am going for the fun portion, I am going to set it up at first to actively track the light source and log the movement to an SD card. After I get a few days of data I will set it up on a timer to move instead of active tracking. When the season changes I will do the logging again and set it accordingly. That is the idea anyway.

Thank you again everyone for your assistance and probably saving me a boat load of fundage.