# Water Level Telemetry



## zephyra (Jan 2, 2008)

Following on from an earlier thread about telemetry and live steam.

I just received a Spektrum telemetry unit ($69) which works with Spektrum RC systems. The unit provides telelmetry for temperature, speed and voltage. Plan is to use temperature as a proxy for pressure, speed for scale speed and find a way of using the voltage telemetry to indicate water level.

I've seen various devices for detecting water levels electrically but most seem to be binary and designed to switch when the water level gets too low. Does anybody know of a way of getting a continuous water level reading that I can convert to voltage. I've tried a resistive sensing wire in the boiler but the results were not good. I also played with a direct measurement of the water level in the sight gauge without much success although I'm sure, in principle, I should be able to use the different refractive properties of light through a tube filled with water as opposed to an empty tube.


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## Chris Scott (Jan 2, 2008)

Larry Bangham experimented with what he called an Electronic Feedwater System for steaming "longevity". He wrote 2-3 articles on it for SitG. I do not remember and cannot get to my SitG back issues to check whether this was low level detection only or low-high level detection. The articles and issue numbers are: 

Continuing Quest for Longevity: #48 
Keeping Water Over the Flame: #36 
Update on Electronic Feedwater System: #61


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## Chris Scott (Jan 2, 2008)

Cheddar made a couple of electronic control systems for the sort of control you're aiming for; EGV (Electronic Gas Valve) and ABS (Automatic Boiler System). When Stuart took over Cheddar years ago they said they had plans to bring these out again but since they have never followed through. I think I have old info on these that Cheddar had on their old website but cannot lay my hands on it right now, it takes a bit of searching. But there is an ancient mls thread that somewhat covers the EGV:


"Proof Of Concept": http://www.mylargescale.com/Community/ForumArchives/tabid/100/Default.aspx?ARCHIVE=true&TOPIC_ID=15320 


You also might try searching the archive for threads containing info on ABS - but be patient while you do, for example 'abs' is the first three letters of "absolutely". 


ABS was closer to what you are trying to do. For water level the crux of it depended on two sensors mounted on the water gauge glass like small collars. They detected low level and the top one high water level. The bottom triggered a pump to bring the water level back up until the top sensor stopped the fill. I do not remember if the ABS was on a loco with an axle or separate pump, or if it worked on either. Nor do I remember how the water glass sensors worked (i.e., resistance, etc.), or the rest of ABS, i.e., water pump, gas and throttle control. Info on these may be in the old Cheddar stuff I have - but no guarantees.


Water level detection has been around for some years with many circuit diagrams on building a boiler probe, but always based on one low level detection probe; most were resistance based one was RF based. 


It always seemed to me that proper water level detection needed (required) two sensors in the boiler backhead for low/high water levels. But the I got push back that an adjustable timing circuit for turning off the pump was fine. On later Accucraft locos Accucraft provided an extra backhead bushing for whatever the owner might want one for and this became available for the probe. But the probe usually didn't correspond to the place you would want a probe. One thread on mls describe using a Jobe(?) bushing that acts like a molly bolt, the back of it spreads out as the bushing is tightened. 


My uneducated(_sic_) idea is that a single very small gauge wire in the water glass, the ends of which is at the low/high water points, could provide thee sensor capability. It's been quite a while since I delved into all this so I'm rusty on my own idea's details. I'm sure someone will graciously tell all I'm crazy







(It's not like it hasn't happened before. It is lonely at the top.







)


Anyway, that's what I remember. I will try to find the Cheddar info such as it might be and forward it to you.


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## A 4 liter V8 eater (May 22, 2009)

I have been struggling with both the issues it sounds like Cheddar solved.


Automatic Boiler Fill:


- one thought is using a float switch to either turn on an electric pump or open a electrically actuated valve to a steam powered pump


-ideally I want the system to be purely mechanical. This would entail a float actuated valve. The float would be narrow enough to fit through a hole drilled in the back of the boiler. The valve would open when boiler water is low and send steam to power a steam engine connected to a small gear pump or diaphram pump. The deadband (slop) in the float actuated valve would determine the difference between high water level and low.


Auto Flame Control:


My idea involves two parallel fuel lines. One (low flow fuel line) has a needle valve that is preset to the burners lowest possble setting. The other line has a valve that opens when pressure falls below 55 psi and closes when pressure reaches 60 psi. One idea is the buy a pnuematic/hydraulic/steam cylinder from Clippard that is plumbed up to the boiler. The mini-ram will control a quarter turn (globe) valve on the parallel (high flow fuel) line. A spring will fight the action of the ram. The tension of the spring will determine at what pressure the globe valve opens. This tension can be adjusted to actuate at different pressures.


-John Maley


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## mocrownsteam (Jan 7, 2008)

BIX ENGINES has what seems to be a neat solution to the boiler control issue. They market what they call a Boiler Pressure Regulator. This Attenuator automatically adjusts the gas burner to keep the boiler pressure at a pre-set level. It seems to be an offshoot of the Cheddar system, but I'm not 100% certain on that.

I got mine from Forest Classics in England. Google Bix Engines and they will come up so you can check out the wbsite. I have not yet hooked mine up as it just arrived a few days ago.

Mike McCormack
Hudson, Massachusetts


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## mocrownsteam (Jan 7, 2008)

Here is the URL. http://www.forest-classics.co.uk/bix029.htm

Mike McCormack
Hudson, Massachusetts


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## RimfireJim (Mar 25, 2009)

For water level sensing ideas, check out these two companies that make industrial sensors: Introtek and Cosense May not work for size or cost reasons, but the technology is out there. I've used one of Introtek's ultrasonic bubble detectors in a work application. It cost $275 (just for the sensor).


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## Chris Scott (Jan 2, 2008)

I have been spinning this around in my head for years - needless to say I have a lot of totally mental material. To me anything that involves modifying the boiler is too complicated - but I don't do boilers. 

I think the best potential lies in adapting the water gauge with the current probe approach. Koso shows a water gauge that has a reservoir tube behind the glass and parallel to the glass. The reservoir eliminates the water adhesion, the water level in the glass is flat, not concave making reading the level difficult. The idea is that you adapt the reservoir idea and add fittings for the mount of two probes that mark high and low water level. When the water is low the bottom level probe is triggered, high the high probe is triggered. I'll leave it to you to work out the electronics. This approach maintains the visual glass water reading with an electronic or telemetry output. 

Another idea would be to adapt the toilet tank float idea to the reservoir. But the details of this seems more difficult to work out than the dual probes on the reservoir. But you might be able to work it out. I haven't spent a lot of time on it as apposed to the dual probe idea. 

Good luck and keep us posted. 

Chris Scott 
Sonoma, CA


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## zephyra (Jan 2, 2008)

I have a new idea - just need the time to try it out. It relies on the different dielectric constants for air and water.

Stick two pieces of condiuctive foil to the sight galss such that each wraps round half the tube but that they don't touch and don't touch the brass fittings supporting the sight glass. You've now made a capacitor and the capatitance will vary with the amount of water in the tube. The dielectric constrant of air is


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## btrippis (Sep 8, 2008)

Chris Scott mentioned that Cheddar used to build an Automatic Boiler Control. They used a sensor on the water gauge to control a servo operated valve to
add water to the boiler under pressure. they used an electronic pressure sensor to control a second servo to control a gas valve between the butane tank
and burner. You can find more information on this in a book by Tom Gorman called Scale Model Ship Propulsion. chapter 14 Automation for Model Steam Plants.
Stuart Models in the UK has finally re-released part of the system. They sell the electronic gas valve part # 34-50-10224 which includes the pressure sensor
for the boiler. The elecrtonics module and the gas valve. The cost is 110 pounds. I have been unable to find any technical info on the sensor they used
on the water gauge glass. It looks like a photo transistor with LED light source to me. I plan on experiminting with this to find one that will work.
Cheddar had one more sensor that was in the water supply tank to indicate a low water level in the tank. I think this turned a light on on the boat to indicate
you needed to head for shore before the water ran out.
Regards, Brian


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