Author Topic: Am I looking for something that doesn't exist?  (Read 848 times)

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Offline WeatherHost

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Am I looking for something that doesn't exist?
« on: April 18, 2018, 06:33:04 AM »
I have a gadget project that uses 12VDC.  I'm trying to use a solar panel to provide power and charge a battery that powers the gadget.  The 15W solar panel provides enough charge to the 8aH SLA battery to keep the gadget powered all day and into the night.  The gadget does not need to be powered all night and could be turned off until Dawn.  Problem is, the gadget draws enough trickle current to deplete the battery before the Sun comes up to power the panel and begin to charge the battery again.  Then it can take a few hours to get up enough charge to make the device functional.  I need the device to work by 7AM or so which isn't happening now.

One answer is to provide a bigger battery, but that's gets kind of pricey.  Another is to scrap the solar setup and provide AC which also gets pricey since I'd have to trench and run wire.

What I'm looking to do is turn the device off at night since it isn't needed anyways.  That would stop the current draw from the battery so there would be sufficient charge first thing in the morning.  I'd like to do it with a photcell controlled relay since I can get those fairly cheap (under $5 usually).  Problem is, all I can find so far are ones that energize the relay at 'dark' which draws current, sort of defeating my purpose of conserving battery capacity overnight.

I'd like to find just the opposite ---  one that de-energizes the relay at 'dark' and energizes it during the day while the solar panel is providing sufficient power for both the relay and the gadget.  So far, no luck.  Either it doesn't exist or I'm not using the right search terms.




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Offline WeatherHost

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Re: Am I looking for something that doesn't exist?
« Reply #1 on: April 18, 2018, 06:39:16 AM »
Another option might be one that provides a pulse at 'dark' and another at 'light' that trips a stepping relay to change state between N/O and N/C.

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Online dupreezd

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Re: Am I looking for something that doesn't exist?
« Reply #2 on: April 18, 2018, 06:41:41 AM »
Use a MOSFET as a switch. You can salvage them out of old desktop computers.
https://www.electronics-tutorials.ws/transistor/tran_7.html

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Offline WeatherHost

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Re: Am I looking for something that doesn't exist?
« Reply #3 on: April 18, 2018, 06:54:38 AM »
Not sure I would know how to make that a real device to connect to.

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Online dupreezd

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Re: Am I looking for something that doesn't exist?
« Reply #4 on: April 18, 2018, 08:07:38 AM »
It is basically a reverse night light. In a normal night light, the LDR and pot will switched around.

You will need to pick the MOSFET depending on the voltage and current draw of the device you want to switch on and off. The 100K variable resistor is to adjust the sensitivity to ambient light.

Hope this help.
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Offline Bushman

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Re: Am I looking for something that doesn't exist?
« Reply #5 on: April 18, 2018, 08:19:18 AM »
If I got this right, you are looking for an NO (normally open) photosensitive relay switch. (Many switches like this let you switch NO/NC) They are all over the place like Banggood, DX, eBay etc. for a couple dollars.  Don't get the ones with LED readouts as they will draw current.
« Last Edit: April 18, 2018, 08:23:39 AM by Bushman »

Offline WeatherHost

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Re: Am I looking for something that doesn't exist?
« Reply #6 on: April 18, 2018, 02:10:27 PM »
You will need to pick the MOSFET depending on the voltage and current draw of the device you want to switch on and off.

Load runs normal on a 12VDC 2A wallwart.  I have a couple of old PCs around if I knew what to look for.  I may even have a small breadboard left somewhere.

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Offline WeatherHost

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Re: Am I looking for something that doesn't exist?
« Reply #7 on: April 18, 2018, 02:12:54 PM »
If I got this right, you are looking for an NO (normally open) photosensitive relay switch. (Many switches like this let you switch NO/NC)

Contacts don't matter either way.  What I'm looking for is 0 load during night.  Most photo relays I've seen are intended to be connected to power full time and turn something on at night.  I'm looking to turn everything off, so that there is as little load as possible even from the photocontrol itself.

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Offline Bushman

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Re: Am I looking for something that doesn't exist?
« Reply #8 on: April 18, 2018, 03:01:50 PM »
So if there is no power, how does it turn itself on again?

Offline Bushman

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Re: Am I looking for something that doesn't exist?
« Reply #9 on: April 18, 2018, 03:11:20 PM »
Looking at the specs of a few, it seems like 30-50 ma is the current draw.  For an 8 aH battery that means 16-24 hours - ignoring wire loss, discharge etc.  Not good enough?

Offline WeatherHost

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Re: Am I looking for something that doesn't exist?
« Reply #10 on: April 18, 2018, 03:13:17 PM »
When the Sun comes back in the morning, battery will still have juice and the Sun will cause the photocell to switch the rest of the system back on.

Hopefully.


I have a few of these:  https://www.ebay.com/itm/K9-DC-12V-Photoelectric-Switch-Sensor-Relay-Module-50mmx25mm-w-2-Cable-/253261304051?_trksid=p2349526.m4383.l4275.c10

But I don't know how much current the relay draws while energized or if it alone would drain a 7AH SLA battery overnight.  If not, it might work for me after all.  I may have to try one and see what happens.






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Offline Bushman

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Re: Am I looking for something that doesn't exist?
« Reply #11 on: April 18, 2018, 03:30:17 PM »
The one you have has red and green LED indicator lights.  If those are always on - then your draw will be higher than the ones I looked at.  I am not sure what the current draw for one (assuming here that only one is on at a time) might be.  You sure you just can't add a battery or use a larger one?

Offline SLOweather

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Re: Am I looking for something that doesn't exist?
« Reply #12 on: April 18, 2018, 03:38:29 PM »
Power a SPDT relay directly off a solar panel. I run a fan in our chicken coop like this. It should work, and it's simple enough to try.

Offline WeatherHost

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Re: Am I looking for something that doesn't exist?
« Reply #13 on: April 18, 2018, 03:44:03 PM »
Power a SPDT relay directly off a solar panel. I run a fan in our chicken coop like this. It should work, and it's simple enough to try.

Hmmmm....  I go into a small solar controller, but I guess I could tap off the connection between the panel and the controller.  I have a couple of small (IC size) relays on hand too.

Might have to try that.  Thing is the raw solar panel output might exceed 20V at times.



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Offline Bushman

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Re: Am I looking for something that doesn't exist?
« Reply #14 on: April 18, 2018, 03:54:50 PM »
A linear voltage regulator will take care of the solar panel.  Like this:  http://www.st.com/en/automotive-analog-and-power/l5150bn.html

Offline WeatherHost

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Re: Am I looking for something that doesn't exist?
« Reply #15 on: April 18, 2018, 04:44:35 PM »
The IC size relays were 5V, so no go, but I did find a small 12VDC DPST that should work.  Not sure what package name, but looks like a typical relay, only smaller.  Rigged a quick mock-up and that might work out.  Since the battery and system will be connected when the Sun is high, they should damp the voltage enough to not smoke the relay coil.

If this works, there will be enough power to operate everything during the daylight, then drop it all out at night while conserving battery to cover during clouds or storms.  For Winter, I'm not sure, but I have brackets to tilt the solar panel if needed.

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Re: Am I looking for something that doesn't exist?
« Reply #16 on: April 18, 2018, 04:48:41 PM »
Not that it really matters, but the gadget is a simple access control system for a pass/walk gate so deliveries and utilities can get in if needed.  They'll never need to get in after dark, so it doesn't really need to be powered at night.

 
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Offline WeatherHost

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Re: Am I looking for something that doesn't exist?
« Reply #17 on: April 22, 2018, 03:21:40 PM »
Busy with other things, but I got the relay put in last night after Dusk.  Light enough to see, but dark enough that the panel was not producing enough energy to trip the relay coil.  I checked around 7 AM this morning and it had not come on, but this is a cloudy rainy day.  Panel looked like it was producing something, but not enough.  Checked again around 11 or so and it was on.

Not sure how much the panel will be able to charge the battery on these coming cloudy days, so it may be a while before I know if the battery will survive the night.


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Offline SLOweather

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Re: Am I looking for something that doesn't exist?
« Reply #18 on: April 22, 2018, 06:31:32 PM »
Thanks for the update. I'm pleased that my goofy idea seems to be working.

Offline WeatherHost

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Re: Am I looking for something that doesn't exist?
« Reply #19 on: April 22, 2018, 06:36:48 PM »
Oddly enough, I had considered that at one time, but forgot about it.  It's simple.  I like simple.  Remains to be seen if it will work better on sunny days.


I have a clock module also that I can set On/Off times, but it has four seven segment LEDs and I'm not sure if that will cause the same issue.

I'm also trying e new solar controller as I'm not sure this one is preventing battery drain back through the solar panel as it's supposed to.

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Offline WeatherHost

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Re: Am I looking for something that doesn't exist?
« Reply #20 on: April 25, 2018, 05:33:19 PM »
Well, it's functioning.  Cycling on at Dawn and off at Dusk.  Not sure how much it will do as far as extending the battery life before I have to change batteries and put one on a regular charger.  Hopefully I won't have to do that any more.

The new Solar Controller has a time on/off function but it's Dusk to Dawn based like everything else.

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Re: Am I looking for something that doesn't exist?
« Reply #21 on: May 12, 2018, 06:23:49 AM »
The relay part is working as intended, switching the unit on at Dawn and off at Dark.

However, the battery is not lasting as long as I'd hoped.  I'm not sure the 15w panel is providing enough current to run the system AND charge the 7AH SLA sufficiently.  I can't see current on the Controller display, only voltage.  It provides enough to run it in full sunlight, but in early morning or late afternoon, or on cloudy days is where I need the battery at full capacity.

Thinking about trying a bigger battery.  I have an old car battery that I use to jump start riding mowers, but won't start a car.  I could put that out there as a test.  If I have to buy a battery, I'm getting up in cost again and I may just be better off running AC.

One other option is POE.  The access control board has a LAN port for programming and other functions.  I have a POE splitter I cold use to pull 12VDC out to feed the system.  I would need an injector though.  I have a piece of LAN cable long enough, but that would mean digging and laying conduit to protect it.


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