SolarGarden Light with BS2

NWUpgrades

I am tring to build several solar garden lights that will eventually be controlled by a BS2 stamp. My first problem is this. I am able to run 5 white LED's from 3V rechargeable batteries. I am trying to use a photoresistor to to turn the lights on at night and off during the day while the solar panel charges the battery. However, I am unable to figure out a simple circuit to do this. Every thing I try seems to turn the LED's on with light and off with dark. I need to keep this as simple as possible, since my budget and eduaction are both limited. I have looked on line and found some help, but everything seems to be more than what I really need. I want to use as few components as possible to do this, as by the time I am done, there will be several garden lights displaying a light show controlled by a BS2.Any suggestions?

Mike Green

Consider using a CMOS 555 timer as a switch to turn the LEDs on and off (www.national.com/ds/LM/LMC555.pdf). It can handle a 100mA load and works down to 1.5V. The timer is triggered by a voltage threshold. You leave out the timing capacitor and set up the photoresistor in a voltage divider with a trimpot so that you can set the threshold voltage where the lights turn on and off. There's a separate /reset line that you can run later to your Stamp with a ground lead so the Stamp can turn off the light (if it's on) for the light show.

NWUpgrades

Thanks for the quick reply. Do you know of a schematic that I can use as an example? I was considering using a 2N3904 transistor with a 1 to 10 k resistor. Do you think that would work? I would like to try and use up parts I have lying around for the testing phase of this project.

Mike Green

You haven't made clear what you want to do. You have LEDs. You have a 3V solar rechargable power source. You have a photoresistor based LED control that works backwards (on in the light / off in the dark). You want to use a Stamp eventually to control things. What kind of schematic do you want? What do you want it to do?

NWUpgrades

I am just looking for a schematic that would explain how to hook up the 555 timer, or one that would use a transistor and resistor to have the photocell work in reverse of what it is made to do, in other words, turn the LED's on when it gets dark and off when it is light. I have also ead about a circuit that uses the solar panel itself to detect the light/dark. I just want to keep it as simple as possible.

ProcessingData...

This is a simple circuit·I found in a book for a Night light setup. (It's Attached)
Sorry that it's in word format ·,·I need to find a good free schematic program.
.:ProccessingData...:.

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Basic Stamp,···· Propeller,·· · SX,·· FUN!


START:·
>Proccessing Data. . . .··
>Task Complete. . .·.
>Saving Data. . . .
>Entering SLEEP Mode. . . .
>Signing OFF

NWUpgrades

Just what I needed. Thanks.

Dave-W

Processingdata,
Download Express PCB with Express Schematic. Works great.
Dave

This is a simple circuit·I found in a book for a Night light setup. (It's Attached)
Sorry that it's in word format ·,·I need to find a good free schematic program.
.:ProccessingData...:.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Dave W.

NWUpgrades

OK, So following the above schematic I am able to get the LED to come on in darkness using the listed resistors and an 2N4401 Transistor. The problem is that I have to use 9 volts. I need to find a way to make this work on 3 volts. Any suggestions as to what to do for that?

wx_eqpt_tech

Been trying for an hour to get this schematic loaded.· This one works on 3 volts.