Snubber diode for float switch?

vtmaps

My spring water comes into my basement by gravity. I pump it with a 115 v AC Shurflo pump to a plastic 30 gallon barrel in my attic. That tank provides low, but adequate pressure to the plumbing fixtures.

Right now I manually control the shurflo pump, but I would like to automate the pump. I have purchased a couple of horizontal reed float switches:
Attachment not found.

I plan to use a circuit like this:
Attachment not found.

The reed switch needs contact protection from the collapsing field of the relay coil, something like this:
Attachment not found.

I have a collection of old AC and DC low voltage wall warts and I need to select one of them and an appropriate relay. Does anyone have any advice about whether to use AC or DC, what voltage and relay to select, and which method of contact protection for the reed switch? My inclination is to use DC because the one snubber diode is across the relay. If I use AC, I will need protection on each of the two switches.

One more detail... the cable from the controller to the reed switches will be about 35 ft long (one way). Will the collapsing field on the cable harm the switches? If that is an issue, how do I protect the switches if I use DC?

Thanks, in advance. (if the images show up as thumbnails, click on them to enlarge)

--vtMaps

waynefromnscanada

Re: Snubber diode for float switch?

If you use a relay with a DC coil, a diode across the coil will protect both reed switches. Just make sure the diode is in the correct position, so the marked end, (the cathode), goes to the side of the coil that will be fed with + voltage. The magnetic field you mentioned around the cables will not be a problem.
The upper section of the lower photo shows the correct way to install the diode.
Cheers.

NorthGuy

Re: Snubber diode for float switch?

A comparable AC coil will take almost twice as much power as DC coil. You can get a DC relay which draws only 0.4W. So, if energy consumption is a concern, DC will be better. Most relays have 12 or 24V coils. It is easier to find a 12V wall wart. Modern ones do not consume any power when plugged in. Or you can run a 24V coil from your batteries.

vtmaps

Re: Snubber diode for float switch?

waynefromnscanada wrote: »

The magnetic field you mentioned around the cables will not be a problem.

good! that's what I wanted to hear

NorthGuy wrote:

if energy consumption is a concern, DC will be better.
Modern ones [wall warts] do not consume any power when plugged in.

Energy consumption of the relay is not a concern, except that it must remain within the 30 VA limit of the reed switch. Good point about modern wall warts... my box of warts are not too modern. I will check them out with kill-a-watt.

--vtMaps

john p

Re: Snubber diode for float switch?

Its an even better solution to use a solid state relay (rated about 3a)to switch the pump. The control voltage is usually between 3 and about 30v DC. And only require a few milliamps to switch it.
Dont have to worry about diodes. And as the required switching current is very small the reed contacts will last almost forever.

vtmaps

Re: Snubber diode for float switch?

john p wrote: »

Its an even better solution to use a solid state relay (rated about 3a)to switch the pump. The control voltage is usually between 3 and about 30v DC. And only require a few milliamps to switch it.
Dont have to worry about diodes. And as the required switching current is very small the reed contacts will last almost forever.

Thanks John, I will look into it. It will need to be a double pole relay, with one pole switching the pump and the other pole switching the relay.

--vtMaps

john p

Re: Snubber diode for float switch?

Vtmaps I dont understand ?with one pole switching the pump and the other pole switching the relay.Switching what relay? They dont come in double pole double throw.All the solid state relays I have seen are just single pole single throw.

Cariboocoot

Re: Snubber diode for float switch?

That puzzled me too.

Float switch controls SSR, SSR controls pump. Only one side need be switched on either. I don't see any need for a double-pole anywhere.

waynefromnscanada

Re: Snubber diode for float switch?

The relay he was planning on using has a second contact he was going to dedicate to holding the coil energized (once triggered by the bottom float switch) until the tank is full and the upper float switch finally clicks off.
So he has a lower switch that triggers the pump to start, and the relay then holds closed until the tank is full and the upper switch shuts off power to the coil.
So he can't use a SS relay without some logic circuitry to control it..
Simplest is to use the mechanical relay as per his drawing.

NorthGuy

Re: Snubber diode for float switch?

Cariboocoot wrote: »

That puzzled me too.

Float switch controls SSR, SSR controls pump. Only one side need be switched on either. I don't see any need for a double-pole anywhere.

I think the idea is as follows:

As the bottom switch dries out, it turns on the relay. One of the relay contacts completes the circuit through the top switch. This keeps the relay closed even when the water sinks the bottom switch and it disconnects. As water goes above the top switch, it disconnects the relay coil. As relay tirns off, it disconnects the top switch. Now, water needs to go below both switches to start the cycle over.

NorthGuy

Re: Snubber diode for float switch?

waynefromnscanada wrote: »

The relay he was planning on using has a second contact he was going to dedicate to holding the coil energized (once triggered by the bottom float switch) until the tank is full and the upper float switch finally clicks off.
So he has a lower switch that triggers the pump to start, and the relay then holds closed until the tank is full and the upper switch shuts off power to the coil.
So he probably can't use a SS relay without some logic circuitry to control it..

How could you beat me by 6 minutes? Do I really type that slow

vtmaps

Re: Snubber diode for float switch?

waynefromnscanada wrote: »

So he has a lower switch that triggers the pump to start, and the relay then holds closed until the tank is full and the upper switch shuts off power to the coil.
So he probably can't use a SS relay without some logic circuitry to control it..

Wayne beat me to it. The circuit I posted in the OP shows it. I can't think of a way to use a solid state relay. --vtMaps

Cariboocoot

Re: Snubber diode for float switch?

Comprende!

So he needs a circuit that will allow a wide range between On/Off. Therefor latching the relay is necessary.

waynefromnscanada

Re: Snubber diode for float switch?

Cariboocoot wrote: »

Comprende!

So he needs a circuit that will allow a wide range between On/Off. Therefor latching the relay is necessary.

You got it!

vtmaps

Re: Snubber diode for float switch?

NorthGuy wrote: »

How could you beat me by 6 minutes? Do I really type that slow

I type fast enough to keep up, but I get my very erratic internet via a 3G cell phone data card, and I live in a valley without cell phone service. Sometimes it works poorly, and other times it doesn't work at all. I've got a cellphone booster en route... should be here any day now.

With dial-up internet I get about 19k with a 56k modem through many miles of copper. --vtMaps

inetdog

Re: Snubber diode for float switch?

vtmaps wrote: »

II've got a cellphone booster en route... should be here any day now.

Good luck with the booster. They will work very well IF there is a place to put the external antenna that gets a good signal. If there is no signal near the house anywhere, the "booster" will do very little good except to reduce the amount of battery power your phone uses while searching for service.
If you have access to the ridge line where there is good signal, then a booster connected to directional antennas on both input and output sides could be a winner. Provided you supply solar power to it. :-)

I am in a dead spot in Verizon coverage, but have cable internet, so a Verizon Femtocell turned out to be the right solution for me. (It implements a tiny cell with connection back to Verizon over the internet, and supports multiple phones at the same time.)
I wandered all over my roof with the booster antenna on a 20 foot pole and still got nothing. At the road 100' from the house the signal was fine most of the time, but that was too much work.

vtmaps

Re: Snubber diode for float switch?

inetdog wrote: »

Good luck with the booster. They will work very well IF there is a place to put the external antenna that gets a good signal. If there is no signal near the house anywhere, the "booster" will do very little good except to reduce the amount of battery power your phone uses while searching for service.

According to the cellphone company's service map I am in a dead zone. But I am using it now. It does work (albeit poorly) inside my house, so I am hoping that the booster will make it work better. The booster I ordered (Wilson Electronics Sleek 4G) will work with 4G as well as 3G. They are upgrading the towers to 4G this year and I am hoping that 4G with its longer wavelength will give me a better reception.

--vtMaps

inetdog

Re: Snubber diode for float switch?

vtmaps wrote: »

They are upgrading the towers to 4G this year and I am hoping that 4G with its longer wavelength will give me a better reception.

If nothing else, it will give you a better data rate if you use a 4G card for that.

NorthGuy

Re: Snubber diode for float switch?

vtmaps wrote: »

I type fast enough to keep up, but I get my very erratic internet via a 3G cell phone data card, and I live in a valley without cell phone service. Sometimes it works poorly, and other times it doesn't work at all. I've got a cellphone booster en route... should be here any day now.

With dial-up internet I get about 19k with a 56k modem through many miles of copper.

I have a similar setup. I use my Android phone to make a Wi-Fi hot spot. It works incredibly fast, but sometimes it just stops working, so I need to reboot the phone etc. My land-line dial-up Internet is 25 to 35k, but it's very reliable. That's why I use it quite often. To get (cheap) wireless Internet, I would need to build a tower. I ask them how come cellphone works without any towers, but they don't have an answer to that.

inetdog

Re: Snubber diode for float switch?

NorthGuy wrote: »

To get (cheap) wireless Internet, I would need to build a tower. I ask them how come cellphone works without any towers, but they don't have an answer to that.

Cell phones use relatively higher power levels at the cell transmitters than wireless internet can.
Cell sites are typically more widely distributed than wireless internet relays
The wireless internet frequencies are more limited to strict line-of-sight than cell frequencies.
There is potentially more uncontrolled background interference on wi-fi frequencies than on cell frequencies.

A lot of factors add up.

In my previous house the only internet option was point-to-point wireless, so I have some (generally good) experience with it. I had my radio unit mounted on a short mast on my roof because I could see the next-hop repeater two miles away through the trees from there. There was only one repeater site close to me, so that was it.
The one interesting observation I can offer is that whenever the point-to-point went down, the response time on Verizon data went from fair to unusable as everybody who had been using point-to-point switched to their 3G backup. :-)

Cariboocoot

Re: Snubber diode for float switch?

inetdog wrote: »

Good luck with the booster. They will work very well IF there is a place to put the external antenna that gets a good signal. If there is no signal near the house anywhere, the "booster" will do very little good except to reduce the amount of battery power your phone uses while searching for service.
If you have access to the ridge line where there is good signal, then a booster connected to directional antennas on both input and output sides could be a winner. Provided you supply solar power to it. :-)

I am in a dead spot in Verizon coverage, but have cable internet, so a Verizon Femtocell turned out to be the right solution for me. (It implements a tiny cell with connection back to Verizon over the internet, and supports multiple phones at the same time.)
I wandered all over my roof with the booster antenna on a 20 foot pole and still got nothing. At the road 100' from the house the signal was fine most of the time, but that was too much work.

X2
We have almost no RF reception here at all. My wife's cell phone barely works with an omni-directional booster. Mine doesn't work at all. Tried one of those "big" boosters with the mast mount antennas - nothing. Not enough signal for it to latch on to. If you're thinking about any such thing make sure they will let you "try before you buy". I think the only signal we get is bouncing off something else (the other mountain probably).

Were it not for satellite, we would have nothing here. Go down the road a few klicks; you've got signal.

NorthGuy

Re: Snubber diode for float switch?

Cariboocoot wrote: »

Were it not for satellite, we would have nothing here.

What company do you use for satellite? How does it work?

Cariboocoot

Re: Snubber diode for float switch?

NorthGuy wrote: »

What company do you use for satellite? How does it work?

Xplornet for Internet. We've had four of their systems (two at cabin, two in town). The first one was actually Lyncsat before they got bought out. This latest one is fine, but pricey. Before that they had a Hughes based system in here and it was horrible.

Had Shaw Direct satellite TV: cost too much for what you got and it wasn't very good quality picture. We now have the Telus satellite TV and it's a bit better bargain and quality. Shaw's cable service was poor too; TV and Internet both. Slow speed, low quality.

NorthGuy

Re: Snubber diode for float switch?

Cariboocoot wrote: »

Xplornet for Internet. We've had four of their systems (two at cabin, two in town). The first one was actually Lyncsat before they got bought out. This latest one is fine, but pricey. Before that they had a Hughes based system in here and it was horrible.

Had Shaw Direct satellite TV: cost too much for what you got and it wasn't very good quality picture. We now have the Telus satellite TV and it's a bit better bargain and quality. Shaw's cable service was poor too; TV and Internet both. Slow speed, low quality.

I had Shaw satellite TV at one time. Technically, it worked well, but content was getting progressively worse while prices were going up. So, we decided we'd be better off without them.

I was thinking about getting Xplornet recently, but they're now bundling their services with Show. I'm afraid they may be bought by Shaw soon.