Solar Panel Project
TerryR
Posts: 39
Hi, I haven't posted anything for some time, but I could do with some help with my project.
That is to rotate a solar Panel rather than buying more panels. I have chosen to use the Stamp BS2 to control the panel's movement and have completed the mechanicals.
I think some photos could help me explain my ideas, but I'm not sure how to post them on this medium?
Need some help. TerryR
That is to rotate a solar Panel rather than buying more panels. I have chosen to use the Stamp BS2 to control the panel's movement and have completed the mechanicals.
I think some photos could help me explain my ideas, but I'm not sure how to post them on this medium?
Need some help. TerryR
Comments
I usually use the "Attach File" button at the bottom.
I added the photo with "Attach File" option.
Yup. Parallax Quadrover.
OK, With these photos one can get an idea of what I am doing. It's a cordless drill driving an M12 threaded bar with an Aluminium Running nut. The Running nut is connected to the panel shaft crank via a push/pull bar, which enables the use of a reasonably short threaded bar.
The right hand bearing is of phosphrabrons from an old domestic meat slicer; interestingly it sits in a gimble and relieves any worries of alignement with the drill chuck. As can be seen I have cut the drill's handle completely off. It is just sitting on a piece of thick rubber matt and held down by a tree saplin rubber belt. Good points with the cordless drill is it's ratchet; anything goes wrong it justs ratchets and no damage is done, also it responds to pulse width modulating and gives good speed control.
I am using the Stamp BS2 OEM for timing. Movement, one would like to get say 180 deg, but with this method that isn't possible.
Relatively there isn't a lot of power from the Sun untill say 9.30 am. It rotates from South East to South West giving good exposure to the Sun from 9.30 am to Sun down. Nothing serious with programing the BS2, I'm simply using it as a timer 30 minute Do- Loop and 1.5 seconds travel time and Retire for Sleep for about 17 hours. All guess work, but seem to be working out ok. I've got it sleeping over night facing West and waking at about 9.30 ish and then returning the panel back to the East stop. Here is the problem the BS2 ignored the East stop and the drill carried on going fortunately it's got the ratched, which we heard.
Fault The end stops are NOT wired with screened cable. Yes, all the BS2 I/O are held high and all In and Outputs are interfaced.
But I could have a better salution if I monitered the Panel position. At present I'm only using four I/O pins so I think I need help to find a way of counting pusles and feeding them to the BS2. Any ideas?
TerryR
Rather than counting pulses - which would probably not work too well with changes in temperature - I would try an accelerometer like this https://parallax.com/product/28017 to read the angle the panel is at and drive accordingly. You only need two pins and it is real simple to read using the PULSIN command.
As a bonus you can use the same sensor to measure vibration, such as strong winds, and program it to automatically move to a safe position.
I would also add a real time clock, the Basic Stamp is not going to be good at keeping accurate time. https://parallax.com/product/29125
In that case you could use something like a Sharp IR sensor to measure the position of the running nut (you have a nice mounting place for a flag). It would also be a good idea to put microswitches at each end for endstops.
I did some investigation on a similar problem, and I found that many commercial units make use of real time clock data and latitude.
For a given latitude, online calculators or solar formulas will give you the sun position for any day-of-year and time-of-day, and so a table of sun position data (or solar formula) can be established for your location.
Complex commercial units will adjust the elevation and azimuth of the panel based on this sun position data depending upon the time value of the real time clock.
You are only adjusting the azimuth, so you could create a much simplified data table and store it in eeprom or memory.
There are many strategies for handling the azimuth tracking.
One simple strategy is an encoder giving one pulse per revolution and a limit switch for the most oblique morning sun position.
By observation establish the angle for one revolution for your setup.
Sometime during the night, return the tracker to the morning limit switch.
At sunrise time, wake-up the tracking and track the sun angle time-of-day from your simplified table of that day-of-year.
Many thanks for your interesting and very good ideas, which I hadn't thought of. You have openned my eyes to gadgets I didn't know existed.
And all at reasonable prices!
I'll study these options, and probably test out most of them and come back with my results.
Thanks again TerryR.
Thank you. Yes your right it is a contraption. I am one of those people who search the garage for anything that will adapt.
The Cordless drill was a light bulb moment. Had not used it for years because of battery problems. No worries with fitting the threaded bar to the drill's hand tightend chuck, but my old lathe did come in handy as the chuck would only accept 10mm diameter, so I needed to turn a couple of mills off the end of the 12mm threaded bar. Yes, the bearing at the other end (from a discarded meat slicer) needed reducing 4mm to fit. I certainly was not out of pocket building this project. Many thanks for your interest.
TerryR
For your application, code it into the BS2 program to stop sending pulses after some maximum time. If the limit switch works, super, and if not, just let the drill click for a little while.
But wouldn't this make more sense to be handled by a PID (+other logic), based on the output of the cells?
Mickster, as a clueless observer you are on the right track there.
Solar panels are very interesting from a control point of view.
Firstly you should get optimum orientation to the sun i.e. the panel must be perpendicular to the sun's rays.
This control can be achieved through well-known solar formulas.
Other methods involve directional l
Secondly, solar panels have a devilishly peaked power curve, so you have to adjust your power draw to find the peak power point, and then track it as the sun intensity varies (clouds, time-of-day).
This is also known as the Maximum Power Point Tracking (MPPT).
This control may be as simple as"'disturb 'n observe", or more sophisticated involving adaptive control, fuzzy logic or PID loops.
The control strategy adopted is an economic trade-off, and only the largest installations will have both orientation and MPPT control.
Adjusting the orientation of the panel to maximize power is equivalent to adjusting the load voltage to maximize power (electronic MPPT). The main difference is one needs to avoid unnecessary movement of the motor.
The crank mechanism doesn't have a totally linear position to angle relationship. Although in practice it might be good enough. An electronic compass could work as a position sensor. It may not because of being mounted near to ferrous metal. The DC current from the solar panel could affect it as well.
A simple solar position sensor can be made by shading some light sensors. As the sun moves, it will illuminate a formerly shaded sensor, signalling that it is time to rotate the panel. A lot of this is complicated by clouds. Some designs compare the brightness of 2 sensors to avoid this.
Many of your suggestions I have in place such as SaucySolition's solar position sensors and Kwinn's idea of a fender washer with holes on its perimeter using an opto isolator method; I have put one on the panel shaft, but I think kwinn's idea of putting it on the threaded shaft is a better idea, as the thread pitch resolution would be 1.7 mm per turn, so here I could use a small magnet and monitor each rotation with a Hall Effect device.
My thoughts are to keep it simple. Yes extra solar panels would do the job, but no exitement in that. I have based my ideas on a couple of perameters. I think the modern Solar panel has quite a good receiving angle, so following the sun "spot on" is a bit over the top for my purpose. I'm looking to have the panel facing South East at about 10 am and moving after a 30 minute pause then moving, for say, 1.5 seconds until it reaches it's South West limit where it will stay until the following morning. For me this is just a challange, I am 83 and bits of me are packing in.
It is programming the BS2 where I need help. What ever happens it would be an advantage for the BS2 to know the position of the panel.
If I decided to count the position of the Panel using say the Hall Effect method would I use the BS2 or would I count the pulses externally?
Many thanks TerryR
If you do go the encoder method; since high resolution is not important I don't think you need to make an encoder wheel, it would be easier to mount an optical sensor facing the drill chuck - with half the drill chuck painted black and the other half reflective.
Another simple idea; mount a row of several micro switches under the running nut, and a semicircular "foot" that will sequentially press down on the micro switches as it passes over them. That would allow for N*2 - 1 known positions for the panel angle. For example, with six micro switches you could have 11 positions, two of them would be at the limits of travel.
Thinking more about the string of micro switches idea (or opto interrupters), you could get much more than 11 positions using six switches (64 I think) - if the "foot" had the right pattern of off and on spots.
Looking at the pictures in the original post, I’d be prone to use a Ping)) sensor to sense the arm position on the threaded rod. Put a mech switch on either end to prevent unpleasant surprises.
I remember working with industrial SCRs these would normally require a single pulse to enable them, but our engineers would apply a train of pulses. So what you have said fits the bill.
To bring the Solar panel to the East Limit, after sleep, My program read:
IF (LmtE = 1) THEN Motor = 0 'motor ON
DO WHILE (LmtE = 1)
Loop
IF (LmtE = 0) THEN Motor = 1 'motor Off
So to give my BS2 more stop signals
I have now put the motor Off instruction inside the loop and kept the outside section too. All working fine, but I don't trust it yet?
TerryR
Oh, and engineers are still doing the train-of-pulses when one will do trick.
Under the counting pulses system-
have you seen the magnetic strip used on fridge magnets.
It can be bought in longish lengths. It has alternating N-S-N-S... poles running along the strip which are easily read with a cheap hall effect switching sensor. I am guessing at four poles per inch.
It is flexible and easily cut.
I guess the snag is the hall device would have to be attached to the running nut on the threaded rod and have a longish flexible lead back to the processor. Not really a problem- bit fiddly perhaps?
Dave
EDIT
I would suggest returning the panel to the east position at the end of the day when the batteries are charged rather than the next morning if possible.
Let us know how your project turns out?
Dave
tritonium. Not a bad idea, but if I can find room on the threaded bar I could attach a magnet and count the turns with a Hall device and calculate the running nut's position.