The SOL project

[Paulus]

The state railway authorities approved the start of a secret experimental project called: SOL
After some advice on this forum a special espionage team gathered information and acquired foreign technology to secretly examine and adapt to own purposes. All for the sake of the nation of course.

Now that was a more interesting intro than just saying I started an experimental solar powered model rail vehicle.
And it is partly true. After some not too successful searching on the internet for information on similar projects (see this topic) and not being skilled in electronics I decided to buy on Conrad a “Solarhouse” and a motor with gearbox. Both kits are from Sol Expert (#40212 “Solarhaus” kit and #90015 “Universal getriebe”). I bought the house kit because it has some electronic unit in it that charges the battery. With a switch you can turn the LED on and off.
This electronic unit is certainly also present in most cheap LED gardenlights of course, but mostly the electronic components in these have no visible codes or markings on it. As I want to examine what components can be used for making a similar charger myself, I wanted something with these codes still visible. I noticed this was the case on the Sol Expert kit. So… a bit of foreign technology was acquired to examine and copy!
Also, the electronics in the kit are easily assembled with nice little connectors which is understandable for me (the KISS principle; Keep I Simple Stupid!) and save me time (and time is harder to buy…).

The plan is to replace the LED for the motor unit that is especially designed to run on the solar cell; 0,6 – 6 volts motor and a 1,2 volts battery. If I keep the model as light as possible, it will work (I hope).

Anyway. Here are some secret pictures of the acquired technology (ssht! Don’t show these to anyone!):


Solar House electronics


Gearbox and motor


And the first fase of the experiment: getting it to work. Until now not much success… There is no live (or better; light) in the LED. Hopefully at the end of the day it will come awake. So I patiently wait and see what will come… otherwise I have to report to state railway authorities…

[Paulus]

Ah and yes.... this is one of the secret components that must be identified. Any help identifying it is much appreciated. I am sure it is just a standard component but I don't have a good clue what it is called and what specifications it has.

[Busted Bricks]

1702 NPN transistor. Google it for spec sheets.

EDIT: No,it's a LED driver: https://www.aliexpress.com/i/32949338594.html

[Busted Bricks]

It doesn't look like there is any charging circuit in that. The solar panel just charges the NiMH cell. The LED driver shuts off the LED when the voltage drops below a certain point. Don't replace the LED with the motor - the chip has some current limiting function. You should run the motor straight off the cell.

The other component on the board is an inductor. The data sheet for the chip can be found here: https://www.mikrocontroller.net/attachm ... QX5252.pdf

You don't really need any circuitry provided the solar cell is not so big it will fry the cell although a diode to prevent discharge in the dark might be a good idea. Read about that here: https://www.electronics-tutorials.ws/di ... iodes.html

[Busted Bricks]

If I was going the solar power route I would probably build a goods wagon or two with the roof full of solar cells and a couple or more large NiMH cells inside. That way you could connect it to any electric loco via a couple of wires. It will be a challenge to have continuous solar powered running unless you have a lot of solar cells available however a decent amount of cells and half a days worth of charging in the sun should give you some useful run time.

[Paulus]

Thanks for your replies. So if I understand you correctly I can charge the battery directly from the solar cell? (Besides the diode you advised me?).
I have some old diodes I once used for a DC 12 volts H0 railway (for safety stops at end of tracks). Could these be used for this?

[philipy]

For the solar powered lighting on my station, I more or less copied the instructions on the YouTube video I referenced in this thread:
https://gardenrails.org/forum/viewtopic ... r+lighting.

Works well and even in the winter in England it powers 8 LED's overnight ( 12 hours) and has been running for 18months without a break. The key is to use a nominally too high voltage PV cell (5v) charging a 1.2v NiMh battery.
The little black component on your circuit board is, I think, a variation on the QX5252F LED driver which is available from ebay and which I used.

[Busted Bricks]

Best to use a schottky diode as they have less voltage drop. Any normal diode will work though provided the solar cell voltage is high enough.

As Philipy said, don't worry about using a 5V solar panel with a 1.2V cell. Unless very big, the solar cell will not provide enough current to do any harm.

[Paulus]

Thank you both. Thanks for the link to the Youtube video.

I will experiment some more the next week. The strange thing is the LED does not give light but the battery seems charged after one day in the (cloudy) daylight. I coupled the motor to the battery and it spins normally. So... I think the LED is defect?

[philipy]

So... I think the LED is defect?

...or connected in reverse, or you've connected the diode in reverse?

[Paulus]

Ah no... it works now!!
I think I did not cover the solar cell enough when testing it this afternoon.
Now it is darker and when turning the cell the LED goes on ;-)

[Paulus]

I like the suggested idea about multiple cells in a freight car and using a larger battery to power an engine actually.
Perhaps something for a next project. For now I think I'll go on with this setup and make a small draisine or something.
Like these small Billard draisines:
https://en.wikipedia.org/wiki/Billard#/ ... ard_RB.jpg
https://philippenoisette.photoshelter.c ... vs31dFK4z0
https://i.pinimg.com/originals/49/30/e3 ... 541a69.jpg

[Paulus]

I don't like the prototype of the solar draisine... too modern ;-) But it exists!
https://www.solardraisine-ueberwaldbahn.de/

[Paulus]

Finally found some time to work on this project last week. The Sol Expert motor kit was pretty simple and straightforward to build. The instructions are clear. You can choose between several gear ratios. The kit comes with a little wooden template to adjust the motor gear in different position depending on what gear ratio you choose. I added a bit of silicon grease to let the gears run more smoothly.





The axle that came with the kit was a bit to thin for the LGB wheels I wanted to use so I made a spacer from a piece of styrene tube. It works but I am not totally satisfied because one wheel has still a bit slack. Perhaps I will replace it in the future with a brass spacer. But for now it is good enough.



And the end result; motor, axle and wheels all in place and looking just fine. Now I really need to figure out how to make a simple chassis...

[Paulus]

The plywood parts of the Solar House kit turned out to be very handy as a support for the motor and gearbox.With a bit cutting and filing all fits nicely. This base is 72,5 mm in square. I will use some balsa sheets that I have lying around to expand the chassis. It will become somewhere between 130 and 150 mm in length, just what looks fine and runs well. The plan is to build something that looks like one of those nice French Billard draisines. Just have to figure out how the second axle will be mounted but there is forming a vague idea for it in my head already.

For now:

[tom_tom_go]

The prototype body looks fairly simple to replicate so it should work well to house everything you need.

[Paulus]

Thanks for your reply. Yes I suppose it will fit al under the passenger bench hopefully.

Some progress on the chassis. I used an other plywood part leftover and and a sheet of balsa on top.
Also made an axle mount out of styrene sheets. Again all very basic and light.






Temporary set up without the solar panel:

[Paulus]

And a successful testrun!

[Paulus]

Best to use a schottky diode as they have less voltage drop. Any normal diode will work though provided the solar cell voltage is high enough.

Can a LED also be used for blocking diode to prevent discharge? It is a Light Emitting Diode so I suggest it could?
That would be practical as I can use it as light
Or would that LED only be working when charging?

[Busted Bricks]

The forward voltage of a LED is a lot higher than that of a normal diode so probably not a good idea. You would also need a current limiting resistor in the circuit so you don't fry the LED.