Photo diode/Reed switch question

[Dandy88]

Is it possible to use a photo diode and nc reed switch to turn off a 6 volt dc battery pack?
I have a windmill with two 6 volt lights and 2 reed switches alternating the lights. I want to turn off the battery pack in the daytime.
Thanks for any help!

 

[Reloadron]

If you want to turn something on or off based on ambient light then yes, a photo diode, LDR (Light Dependent Resistor) or other photo type sensor would work. I assume the windmill is a small motor driven device? You mention a NC Normally Closed reed switch? That would mean the reed switch opens in the presence of a magnetic field? I won't say the reed switch is the best on and off device for the windmill, there are likely better and easier ways to turn it on and off with a photo sensor. Do you have a schematic or drawing of exactly what you have?

Welcome to the ETO forums!

Ron

 

[Sceadwian]

I think he means a DC controlled reed relay Ron, not a magnetic driven one. I'm guessing that he means the photodiode current would trigger the relay? Which can't happen the current they produce is tiny, anything using them would need an active transistor amplifier to trigger the relay. But I'm just going based on what's been said and there aren't a lot of details.

 

[Dandy88]

I assume the windmill is a small motor driven device?

No. A magnet is on the blade hub so its strictly wind driven.

Thinking about the nc reed I would think that would take a more complex circuit.
You mentioned an on or off using a photo diode. I always thought these conducted with a light source. If I can get one that is normally open when light hits it then that should work. These diodes are much cheaper than a DC photocell as well as being smaller. They would also be much lighter and easier to mount on the fin.
My 6 volt battery pack is out of an old toy. The setup works fine but I would like to save on battery time. Ill attach some photos. Thanks Ron!
**broken link removed**
**broken link removed**

 

[Reloadron]

Well a picture is worth a thousand words. My image was a small toy battery driven windmill with a few LEDs. A magnet would pass the reed switches and the lights would alternate. Wow, did I miss that one. Sceadwian was closer than I was.

OK, now if we just want to turn something on or off based on daylight a simple and small photocell circuit will do that. There are a number of ways to go about it. Using a simple comparator circuit like those found here would be one way. Scroll down to the Photo Cell circuits on the linked page.

Another option even simpler that I have used is just a LDR photocell in series with a small relay. The relay being capable of switching a few amps load. This uses a NSL-5910 Silonex Photo Cell and a small relay. Matter of fact I mentioned it in this thread. The relay was one of these, a 2BC-1B-107D. There are other relays that would work.

Ron

 

[Sceadwian]

I always thought these conducted with a light source.

Nope, you might be thinking of a photo transistor. They only have two leads and can look like diodes (with a window on the top) the light striking the exposed base junction causes the transistor to turn on, all that's generally needed is a bias resistor to control how much light has to shine before it turns on. It's not going to be very thermally stable though.

 

[Dandy88]

Thanks for the clarification Sceadwian! Even though Im a retired electrician I only have a cursory knowledge of these devices.
Ive tried searching for the type of relay Ron posted. Apparently the U.S company that carried these are out of business. Can someone recommend a relay I need from somewhere else. I looked at this one but with my unfamiliarity it doesnt seem right. I liked the can type that Ron showed. Seems it would weather better.
Thanks for the help everyone!

 

[Reloadron]

The relay I mentioned was just a 300 ohm 23 mA coil relay. Just about any relay designed with about a 5 volt coil should work. While the hermetically sealed can relays are nice, they do carry a hefty price tag. If you want one of the one I mentioned and can get the photo cell I mentioned I'll send you one. I have several slightly used that I'll never use during my lifetime. It's yours free if you want it. Just PM me a mailing address.

Ron

 

[Reloadron]

Got your PM, no problem at all. Attached is how to set it up. I suggest the 1N4002 as shown. I explained the relay pinout in the PM I sent. Just drop me a PM when it gets there. If you want to change the sensitivity (Light / Dark) just add maybe a 100 ohm pot in series with everything or maybe a 1 K pot but first try it as drawn. I am tossing in the LDR also. Enjoy and have a nice holiday season.

Ron

 

[Mr RB]

Try a hall switch, Honeywell SS441A.
Datasheet;
https://www.electro-tech-online.com/custompdfs/2011/11/c20008.pdf

It has 3 legs;
* ground
* +ve power (anywehre from +5v to +20v is fine)
* output (output connects to ground when the magnet is present - similar to a reed switch)

These hall switches are very nice, they have internal brains that give very clean switching. Think of them like perfect reed switches that never wear out! The only difference between the hall switch and the reed switch is that the hall switch has an extra pin (the +ve power input).

 

[Dandy88]

My apology's for not getting back sooner. Been painting the house and remodeling the back porch.
Ron I received the relay this week. Thanks again!
Rb I checked out the hall switch and that looks better. My wife asked me what I would like for Christmas and an Electronics trainer was one of them. Good way for me to learn about these low voltage devices.
Thanks Guys!

 

[Reloadron]

Glad the relay and photo cell made it there.

Ron