Solar power

Hi Guys!

Like I said "weird topic" (what else do you expect from me?) but my tram layout was originaly envisaged as a "plank" to fit rhe front of my caravan so 12 volt DC was guaranteed. Then things got a little complcated starting with us getting a different 'van and the layout would no longer fit. So I tried to see if it would be possible to fit something else in in its place and I found that I have room for a single oval of N gauge. I got an N 0-6-0 tank engine, a couple of beer waggons and a guards van. Glued some track down to a board and "Hey Presto" minature layout.
Now the fun bit, It runs great using a transformer/controler when we are hooked up to electric on site. When mated to my 13Watt solar panel in moderate sunlight the train rumbles round (I need to mount it on some polystyrene or something to deaden the noise) quite happily. In bright sunlight it whizzes round and I will need some form of controler/limiter to keep it safe as I do not wish to repeat the experience of having my toast shoved into my lap by a derailed train. However in dull conditions the engine simply sits there and makes a high piched whine.

What I need is a schematic for a 12 volt input controler and to know if it will cause any damage when there is insufficient voltage to actualy move the train.
I can always simply hook the solar panel up to a battery to provide a power source but that takes away the random element of when the train will run and I still need the speed control.
Can anyone help?

Regards
The Bankie

It all depends how random you want!

You could create a charging circuit for a set of
capacitors, so once they are charged, they set
the train off for a set time.

The speed could be limited by resistors (or
something!), once the charge has been used,
it can recharge at the rate the solar panel allows,
meaning a period of running at a set speed and
for a set time, but you would not know when it
would start again.

Hi Jeff :)

I had thought it would be sonething like that but not being an electrical wizard I need some answers. For example what size would the capacitor or resistors need to be. How do I get the resistors to operate only when the speed is excessive as straight resistors will simply reduce the output over the entire range. Capacitors will work whilst producing a diminishing output so that would be ok but how do I get them to stay charging untill fully charged before releasing the charge?
Random in this case means runs when the sun shines above weak sunshine and stops when it falls below that.

Thanks for the consideration and reply.

Regards
Jim

Terry said

I'm afraid you should picked up on the '(or something)',
I put it in brackets purely because, like you, I have no
idea how to do it!
I suggest you join MERG, or at least have a chat with
someone who is a member, because if it is possible,
then they will know how to do it, and probably give
you options as to methods as well as variations that
might be possible.
Either way, it is an interesting approach for running
a model railway, in an unusual location, good luck! 

Hi Jeff
I'll post how I get on when I get further along the route. If nothing else it will be fun.

Regards
Jim

I am no expert but I would have thought that as the standard train set controllers run off a separate AC/DC power supply all you would need to do is plug you solar panel into the train set controller instead of the AC/DC power supply and you would then have speed control when the solar panel is proving enough charge.

Hi Campaman
Standard DC controlers tend to have the step down transformer built in but the idea is sound in that I can look for a 12v DC controler for another application (12v LED ligting dimmer perhaps) and see if that will fit.
Unfortunately I suspect that this will reduce the current at the lower level and simply not allow as much current through accross the entire range. I need something which will allow the low level current through and only block the upper level so that the engine will run on duller sunshine and not overspeed in bright. A simple variable "pot" resistor will reduce the top end but I do not know it these things have a lower limit before they start to work.

Regards
Jim

Hi Jim,
Like others, I'm no expert, in fact I probably know just enough about electrickery to be dangerous!
I would have thought your best solution would be to hook up the solar panel to a medium sized battery, like a small car battery?
That way, you're not 'wasting' power when the sun is shining brightly or threatening to burn out your model and you can save some power for night time operations.
As for cost, have a hunt around a scrap yard and choose a battery from a recent car that's been smashed up in an accident. The battery should still be quite new, as long as it's not damaged, obviously.
Google terms like "building a low wattage battery charger" to help with that part of the project.
HTH,
John

Hi Allegheny 1600
A battery is no problem I have two 110amp deep discharge leisure batteries for the van. One in use and one on charge so power is not a problem. It's the random element and without a random power on/off circuit that means I need to manually control it so the random element is lost. This was the reason for choosing to use the solar panel as, without removing my trousers, I have no control over the sunlight.
My next door neighbour has found a power limiter circuit so I will build that and see what results I get.

I still have no answer to the question of whether or not feeding power which is too low to opperate the train will cause damageto the motor. Mainly I am concerned with overheating but nobody seems certain about whether or not long periods of low power will cause this.

Regards
Jim

[user=1339]The Bankie[/user] wrote:

Hi Campaman
Standard DC controlers tend to have the step down transformer built in but the idea is sound in that I can look for a 12v DC controler for another application (12v LED ligting dimmer perhaps) and see if that will fit.
Unfortunately I suspect that this will reduce the current at the lower level and simply not allow as much current through accross the entire range. I need something which will allow the low level current through and only block the upper level so that the engine will run on duller sunshine and not overspeed in bright. A simple variable "pot" resistor will reduce the top end but I do not know it these things have a lower limit before they start to work.

Regards
Jim

I see from looking that the separate transformers actually step down to around 19vAC output to the controller so the controller must change it to DC although not knowing this I have in the past used one of these powered by a 12v car battery and it worked OK.

Hi Andy
What's that line from the Who "Substitute"
"The simple things you see are all complicated"

Regards
Jim

How about a LiPo controller used in radio control of boats, planes, trains. Takes low input of 3.7-11.1 (1-3 cells) outputs 12v.

Nigel

Hi Nigel
Worth a bit of research.
All these suggestions are great I'll be able to find something.

Many thanks to all contributors

Jim