Optical ATO

Request new hardware or ideas for the controller
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slipperysam
Posts: 16
Joined: Thu Sep 29, 2011 6:25 am
Location: England

Optical ATO

Post by slipperysam »

As title will this be a future venture.

sam
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: Optical ATO

Post by rimai »

Those switches are quite expensive.
They cost over $100, for just the switch.
Is there any interest on these?
Roberto.
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: Optical ATO

Post by rimai »

But, while we are in the topic of ATO, I'd like to inform that Avast Marine has a pressure sensitive switch that can be used with RA. They work just like a float switch, but have no moving parts.
Now, for around $100, I could actually get a measuring device that can pinpoint the exact height of your water column, instead of just on/off like a float switch.
So, one could use to measure sump water level or even RO reservoir water level.
Two technologies can be used:
* Pressure sensing chips, which you would have a tube connected to the chip and a submerged pipe and as water rises or lowers, it creates a differential in pressure which can be read by the RA and converted to water level.
* Resistance varying sensor, which would be in a form of a ruler. As the water moves up and down, it varies the resistance, which can also be read by RA and converted into water level. It's made of plastic, for those concerned. Only problem is that it can only measure a foot of water difference, so if you were to use this for automated water changes, you would have to consider how much water you would be displacing.
Which one do you think you be more appealing?
Roberto.
rygh
Posts: 21
Joined: Wed Jun 08, 2011 5:07 pm

Re: Optical ATO

Post by rygh »

Having a true level sensor would be great!
The exact technology does not matter to me
You can consider acoustic as well, since the micro-controller may be
able to do the "smarts", and all you need is transducer.
That would bring the cost down.

What matters to me more is accuracy.
To do what I want, it really helps to have 1/4" or 1/8" accuracy.
Well - repeatability to that. Exact value does not matter.
rygh
Posts: 21
Joined: Wed Jun 08, 2011 5:07 pm

Re: Optical ATO

Post by rygh »

Thinking more, that resistance based ruler sensor is probably best.
(I assume you mean something like eTape)
In theory you can get custom lengths, but probably need large volumes.
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: Optical ATO

Post by rimai »

Yes, something like eTape. Both solutions should be pretty accurate.
I like the eTape too, but I don't like the way the contacts would be exposed.
I'd need to work out a way to make it waterproof somehow.
Roberto.
chercm
Posts: 17
Joined: Wed Jan 25, 2012 6:15 pm

Re: Optical ATO

Post by chercm »

if there is such a one , it will be great
TanksNStuff
Posts: 188
Joined: Fri Dec 30, 2011 6:57 am

Re: Optical ATO

Post by TanksNStuff »

I first was interested in this thread due to the mention of the Avast Marine pressure sensor because I have the "standard" ATO kit and was wondering how I could convert it to the digital output so that I could utilize RA to send me a message when it triggers a "High" reading.

However, after reading the rest of the posts and realizing the possible need for a level detection system... I did a search on ultra sonic level transducers and stumbled upon these:

http://www.ecrater.com/p/11851880/ardui ... le-hc-sr04

These are relatively cheap (around $9 each) and are made for Arduino!

Here's a video that might be able to give you some more info on it:

http://www.youtube.com/watch?v=2v_0lJApb3s

I'm not sure how it would react to water surface but it might be worth looking into.

Or, maybe something based on sonar like these for around $25-$30 each? :

http://www.pololu.com/catalog/product/726
rygh
Posts: 21
Joined: Wed Jun 08, 2011 5:07 pm

Re: Optical ATO

Post by rygh »

Just an FYI:
I hooked up the eTape level sensor, using a simple resistor ladder and an analog input.
The results were not horrible, but I would say it was disappointing.

It is not particularly accurate. Lucky to see a 1/4" change.
It also has a lot of noise in the signal. Could be my design though.
But the error is larger than that 1/4" drop, so probably needs a lot of averaging.

It also does not work to the bottom end of the scale.
So really only usable for about 4" of depth or so.
I verified that with a high quality ohmeter.
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: Optical ATO

Post by rimai »

Great info.
I got a sample of those to test, but never had the time to do anything with it.
What value resistor did you use?
Roberto.
rygh
Posts: 21
Joined: Wed Jun 08, 2011 5:07 pm

Re: Optical ATO

Post by rygh »

I used a 2K.
That is what they recommended in their app note.
I think it would work better with a lower value, but
it is not clear how much current this thing can take.

I may still put a cap on it, in case noise is from power supply.

Note that I sealed the contacts with shrink tube and silicone, but they had
what looked like a small vent hole, which I left open.
lucho
Posts: 80
Joined: Fri Mar 02, 2012 8:11 am

Re: Optical ATO

Post by lucho »

Hi, I am really interested in this as a way to measure the lever in my reservoir. Not sure if someone could make this work. The other question I had (since I am new and am considering getting the RA) is if you need to use one of the 2 ATO switch plugs for this.
thanks
rimai
Posts: 12881
Joined: Fri Mar 18, 2011 6:47 pm

Re: Optical ATO

Post by rimai »

I have no progress on this
Roberto.
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