solar switch: need help

[mettam]

I am trying to build a solar switch that turns the light on at night and off durring the day.

I am using one transistor that at night the transistor turns on because no current it going to the base and then during the day the light turns off because a current goes to the transistor.

Please look at the attached image to see how I have breadboarded it I hope you will be able to tell me what I am doing wrong.

Thanks in advance

Justin.

 

[audioguru]

You forgot to attach the schematic with parts values so we know what the circuit is doing.
You forgot to tell us what is the problem. It looks like it works.
Don't you want the solar panel to charge the battery during the day?

 

[RadioRon]

In your photo, it appears that you have the solar cell leads both plugged into the same terminal and therefore shorted out and doing nothing. It also appears as if you have no current limiting resistor in series with the LED, so I will assume that you are using one of those LEDs with the resistor built-in. This circuit might work if you are using a FET and you apply the solar cell voltage with the right polarity. Can you provide any more info?

Also, I don't recognize that solar panel but I hope it has more than one cell in it, because one cell only gives about 0.5 volts which isn't enough to bias off the FET.

 

[mettam]

You forgot to attach the schematic with parts values so we know what the circuit is doing.
You forgot to tell us what is the problem. It looks like it works.
Don't you want the solar panel to charge the battery during the day?

I don't have schematic drawing software.
The parts are just a LED a Transistor (what kind I don't know) and a 2V 200mA solar cell.
Yes I will have the panels charge the batteries during the day.
The problem is that when I put light on the Solar Panel the LED stays on and it should go off.

I thought maybe the solar panel didn't produce enough power even in a lit room to effect the transistor but when I connected a 4 Volt battery to it it still didnt work.


I drew my inspiration from this site.

 

[mettam]

In your photo, it appears that you have the solar cell leads both plugged into the same terminal and therefore shorted out and doing nothing. It also appears as if you have no current limiting resistor in series with the LED, so I will assume that you are using one of those LEDs with the resistor built-in. This circuit might work if you are using a FET and you apply the solar cell voltage with the right polarity. Can you provide any more info?

Also, I don't recognize that solar panel but I hope it has more than one cell in it, because one cell only gives about 0.5 volts which isn't enough to bias off the FET.

No the LED doesn't have a current limiting resistor built in.
I have pluged the solar cell terminals into the Transistor in a number of different configurations the photo does show both the + - going into the base but I have had the + to base and - to emitter,
I didn't see any need to put a resistor in series since the load can handle the source without heating up.

Sorry if my aproach is ridiculous as I am a newbie to electronics, its hard to teach myself electronics with out any one to show me stuff.

 

[ljcox]

I don't have schematic drawing software.

I use either Powerpoint to draw circuits or simply draw it by hand and scan. Do a search of my posts and you will see examples.

The circuits shown in are fairly basic and need to be used with caution.

You need resistors in series with both the base and collector in order to prevent the possibility of damage to either the transistor or the LED.

 

[audioguru]

Your LED stays on?
Then the transistor might be destroyed because your circuit doesn't have a resistor in series with the base to limit the current and does't have a resistor in series with the LED to limit its current, or the transistor is the wrong kind. How do you know which pin is which on the transistor? Maybe the pins on the transistor are in the wrong place, so it is acting like a diode.

Do you see that your solar cell has both of its wires together so is shorted?

Your battery looks like 3 AA Ni-Cad or NI-MH rechargable cells that are in series making 3.75V. It cannot be charged from a solar cell that has only 2V.

I use Microsoft Paint program to make schematics by making a few straight lines with the Shift key down then using copy and paste to get parts of other schematics or datasheets.

 

[mm0935]

If add a cap. in parallel to and a diode in series with Battery, is it work?

 

[audioguru]

If add a cap. in parallel to and a diode in series with Battery, is it work?

Adding a capacitor and diode won't fix the problem of the base and collector of the transistor don't have current-limiting resistors, the solar panel is shorted or the transistor is connected backwards.

 

[Sceadwian]

mettam, you need to re-read Radio Ron's post above.

 

[mm0935]

sorry! I was side trace.
yes, The terminals of solor cell seems connected in short circuit.