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Unread 21st May 2015   #1
harrym1byt
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Caravan Level indicator

I am sure I posted the design for this little beauty of a gadget, long ago, but now I seem unable to actually find it. I am therefore reposting it. I will gradually fill in the details, as I find the time.

A DIY Caravan Electronic Level Indicator by HarryM1BYT

I think we all struggle to get our vans level and the usual fix is a spirit level, which is difficult to see, only serves one direction at a time and to enable your drains to work properly, you may want it to be other than absolutely level. This gadget allows you to pre-set what ever version of level, suites you and the van and reproduce it quickly and precisely, each time you pitch on site. I've been using it for many years and it makes setting up much easier than guessing, or using a bubble level. Its simple accuracy means you can get it spot on much more easily and a lot quicker, even in the complete dark.... No shouting up a bit, down a bit, just watch the display hanging in the front window.

Please don't reply mentioning filling pans with water, using bubble levels, or Iphones etc. None of them work as quickly, as easily, or as simply as this and yet with such reproducible accuracy year in year out. Calibrate once, get the same version of level perfectly ever after.

This project started as a means to be able to get a more accurate and reproducible level easily visible from out side the caravan, in both daylight and after dark. I originally devised the idea 40 odd years ago, but only got around to testing it around 2004. My original idea was to use small 12v panel lamps, but LED's make it much better.

The project turned out to be fairly easy and produced much better results than anticipated. The only part which might prove difficult to source is the brass bob weight. I turned this up on my lathe from solid brass rod, to suite the purpose, though you might be able to find alternative parts to produce the same result. The critical thing is that the weight should hang perfectly straight.

Its fairly easy to understand, no electronics involved as such. There are two modules to the project, the sensor and the display, the two needing to be linked via a fairly flexible 6 core cable. The 5 core plus screen cable, as used for an old wired PC mouse is perfect for that purpose, assuming the screen wire is used for the ground connection.

The sensor is simply a brass bob weight, suspended via a thin copper wire inside a short length (about 6") of 20mm plastic electrical conduit plus an end bush, making contact with any two of four brass screws - the ends of which are ground to a sharp point. This module is installed wherever it can be fitted rigidly and not be disturbed once calibrated. I fitted mine in the front top locker of my present van, where I was able to pick up a 12v supply from the radio. If no 12v supply is available, then it could be powered from a 9v PP3, or similar.

The sensor is linked to a small plastic box providing a display of five LED's. This part is not fixed, but just hooks onto a blind in the caravan's front window when it is needed. When not needed it can be stowed back out of the way inside the locker.

Building the sensor...
I used a 6" length of 20mm plastic conduit with a 20mm end bush, as a means to reinforce the bottom where the four pointed 4mm contact screws fit. I drilled undersized holes through the thickest part of the bush plus pipe and tapped them. Due to the nature of plastic, despite tapping it the grub screws will still be quite tight in the threads and stay put where they are set. I made a bob weight drilled and tapped for a 4mm brass screw, then drilled a tiny hole down the centre of the screw, soldering the suspension wire in the screw. The suspension copper wire, needs to be the very finest you can find, with an absolute minimum of desire to curl itself. I found the wire used to link phone hand sets, to the wall socket, the best.

I used a similar plastic bush with a turned brass centre was a perfect fit for the top of the pipe and a tiny hole through the centre of this, allowed the wire to pass through it and down the outside of the pipe to a drilled brass screw. A 6 way cable (old mouse cable) links the sensor to the display.

Once built, the four screws are adjusted to the point where the gaps between the screws pointed tips are almost touching the bob weight all around, with the bob weight in the centre. Basically screw them in gently to the point where all four LED's light, then ease them back out a fraction of a turn, until only one LED is lit per direction.

There is nothing at all critical about the need for sensor to be 6" long.

The plastic tube, is then mounted on a triangular plate via the conduit bush end. 3x springs and bolts, holding the two plates together, then allow the unit to be precisely calibrated to your own desired version of level.

For the display, my latest version just reuses an old cassette tape case. I am presently sourcing a better case, but it makes no difference to the design. Five 5mm holes are drilled in the face, for the LED's. The LED's leads then formed a firm base onto which to solder the rest of the components. Once it has been tested, hot melt glue dribbled over the parts then keeps it all secure inside the case.
For the 12v supply a fused source should be found, or a fuse added - though the possible short circuit current is limited by the 4x resistors in parallel.

Once built tested and working, the sensor can be installed in its chosen position. I used heavy gauge double sided tape, to fix the triangular base in place. I then got the caravan perfectly level in both directions, made sure the drains worked correctly, fine tuned the best level, then watching the display I calibrated the sensor via the three sprung bolts, so as get the display to indicate level.

In use, for instance to set the side to side level, you watch the LEFT and RIGHT LED's. The LEFT one lit means that the left side is high (high = light = lit). As the caravan is adjusted, the two LED's will flash alternately due to bouncing between the opposing contacts. The one which is lit more of the time is the high side. Once the period of both is about the same, the caravan is side to side perfectly level. The very slightest of taps with a finger on the side of the caravan sets the bob weight rocking and LED's flashing. This unit is extremely sensitive, far more sensitive than might be needed and this should be kept in mind when levelling.

I originally thought that oxide build up on the brass of the bob weight and the contact screws might pose a problem, but giving this a little more thought - The movement of the caravan on the road will help keep these perfectly clean.

Schematic

Wiring Diagram and components.


In the above diagram, on the left is the display, with the sensor on the right.

Parts list
5x 390 Ohm
4x 100 Ohm
1x 1N4000
4x Superbright white LED
1x Suprerbright red LED
1x Switch
6 core very thin flexible cable (ex-mouse cable?)
1x black plastic box http://www.ebay.co.uk/itm/ABS-BLACK-...:X:AAQ:GB:1123
1x 6" of 20mm plastic conduit
1x 20mm conduit bushend
4x 4mm brass screws made to a point contac + 1x for below.
1x brass weight about 50mm x 12mm, with an accurately centred 4mm tapped hole in one end for suspension.
2x triangular allow mounting plates, 3x 5mm bolts, 3x 5mm nuts, 3x springs - for the base.


This is the brass bob-weight, turned up in the lathe. It needs to be slim enough to fit in the plastic tube and between the four contacts The RH end was drilled and tapped to accept a 4mm brass screw. The brass screw I drilled through the centre with a 1mm drill, to accept a suspension wire. I made a second similar screw, which screws into a tapped brass insert which was itself turned to fit neatly inside a 20mm plastic bush (the black object on the right). You can just see the brass insert poking out of the plastic bush.



The suspension of the bob-weight is crucial to its accurate operation. It has to be centred, both top and bottom and the suspension wire needs to be conductive, thin and very compliant, so as not to disturb the hang of the bob-weight. Network cable is too rigid and will want resume its curl. I used a single core from the telephone wire, as used to link a phone to the socket at the wall. This type of wire has the copper strands mixed in with nylon, which makes it very strong, but very flexible. The downside is that it is very difficult to solder, but not impossible. When soldered it will have the two screw heads facing each other, ready to screw into the bob-weight at one end and the brass bush at the top end. That is stripped at either end, then passed through the 1mm holes in each screw head, then the ends soldered at the far end of the screw from the end (the threaded end). I set it up so the length of the suspension wire, hung the bob-weight with 2/3rds
below the contacts, 1/3 above the contacts.

The latest base, is now a tripod with three adjusters to set the level up. The two triangular bases are made from some scrap alloy sheet. The lower of which has to be fixed into a suitable place in the van, the van then set at what ever level works for that particular van, the unit is then finally calibrated to the van. The idea is not one of getting the caravan precisely level, but one of being able to quickly reproduce the version of level which makes your caravan work best.



I've used crimp on bullet connectors, which happened to be a perfect fit on the contact grub screws. Rather than adjusting a top and bottom nut, I have used three springs pushing the two triangular plates apart and tight against the top nut. The vacant holes just above four contacts points, serve no purpose, it was just an attempt to use an alternative contact method, to the one I settled upon.




Here you can see one of the four grub screw contacts. These are tightened up so as to leave an absolute minimum of gap between their tips and the bob-weight, with the weight centred in the tube. The bob-weight obviously needs to be able to move, but only slightly.





Sensor Unit mounted in place. The tubular object is a specially made spanner to allow the tripod base to be fine tuned to level.



Here is my MKI and larger sensor, just to show the idea - it shows the weight and the four contacts.



Here is my latest version of the display, in a neat little box.
LED lit, means that side/end is too high. Opposing LED's lighting up for similar periods, means level. No PCB is used, just the components supporting the leads - 'dead bug' style for a simple one off build.




A cord allows it to be quickly hooked onto a blind, in a front window. The switch allows it to be turned on and off. The red LED in the centre, just provides an easy reference point for the eye, when trying to level in absolute darkness - as well as a power on indication.




This is it, hooked onto a blind, how it would normally be used. The window had to be opened wide, due to the reflections of the sun from the window lens. Upper LED lit, means that the nose of the van is too high. The Left LED lit, means the left hand side of the van as you are looking at it, is too high. In actual fact the front is around 2" high and the left around 1/4" too high. LED LIT = HIGH





Here is a video.

It is so very sensitive, I was putting 1mm thick alloy sheet under the tyre, trying to get it to show level and even that was proving to be too thick.

The starting point of the video is very close to actually being level, no more than a few mm out in both directions.

0 to 17 seconds - get the van side to side level. Left one lit shows left side is too high, drive it onto a 6mm thick bit of wood - but still a touch low on the right, less than 2mm difference side to side.

17to 36 - adjust the end to end level. Top one lit, shows front end is too high, lower it with jockey wheel until top and bottom LED's flicker on and off about equally. Idea is not to get two opposing LED's off, or both on, but just on for roughly equal periods.The camera position is static, if you watch the van rise and fall just mm between 17 to 36 sec. you can see just how sensitive it is to out of level.

A long way from level, one LED will remain lit solidly. As level is approached, the two opposing LED's will flicker more and more, until they flicker equally when level. Lit = too high at that end, or that side.

Remember it is capable of far more accuracy than might possibly be needed for levelling a caravan, but too much accuracy is better than not enough.




This most recent version is as yet untested for accuracy, but I did carry out some accuracy and repeatability tests on my original version and I have no reason to expect the accuracy of my MKII version being much different from my original. The results were really quite surprising....



For test and calibration purposes, I used a mag-mount LCD engineering level, which reads to 00.00 of a degree - 2 decimal places. I only tested the fore and aft accuracy, the side to side will be the same, but not so easy to test. The process went as follows...

1. Switch unit on and level the van end to end as near as I could get it, as indicated by the unit. In fact the indication was slightly more accurate than I was able to adjust it to, using the jockey wheel height adjustment. It is so very sensitive.

2. Set my mag-mount angle unit on the hitch, switch on and calibrate it to zero.

3. Lower the nose of the van to the floor, raise it to maximum, then adjust back to level as indicated by my unit. Finally take a reading from the mag-mount unit.

I repeated step 3 only a total of four times and noted down the errors between HR Unit and my fancy mag-mount unit, these are the results....

Round 1 00.09 degree error
Round 2 00.13 degree error
Round 3 00.01 degree error
Round 4 00.08 degree error


I had originally expected it to work to an accuracy of 1 degree or so, but the above results are quite astoundingly accurate for such an apparently crude device. My latest version like the version installed in my van, is so very sensitive that despite being set on a heavy bench in my workshop, which itself is set on several tons of concrete, but we have a main rail line 100 yards away. As trains pass, it sets the bob-weight in motion and the LED's flashing.

I find it difficult to express just how well this simple concept works and how much time it saves in setting up. I have been able to set up on site and get it perfectly level, without any assistance at all now for 6 years. I just put the display in a front window, put a ramp under the low side, then drive it up or down the ramp until it shows level. You can see the display in your rear view mirror, though I use my mover. Then adjust the end to end level via the jockey wheel, whilst watching the display. Remember all you are trying to do, is get the two opposing LED's, flashing at around equal on periods, as the weight, bobs about between the two opposing contacts.
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Unread 22nd May 2015   #2
MicknPat
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Whilst in the US I recall seeing a device similar to this one called the RV EZ level to check the level of your motorhome or caravan.

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Unread 22nd May 2015   #3
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Quote:
Originally Posted by MicknPat View Post
Whilst in the US I recall seeing a device similar to this one called the RV EZ level to check the level of your motorhome or caravan.

'Factory calibrated', which means it will just get your RV level and the bit of RV where it is placed level and it doesn't spec the actual accuracy. It only suggests it will get your bed level and your fridge will work. I demand much more than than, I want my shower, sink and w/basin to drain well, besides the other obvious things.

RV's and caravans have lots of surfaces and if you ever checked them, they vary quite wildly, none of the flat surfaces actually agree with each other. So where you put it is important, but even then, it might not be a level which works for your shower drainage. My sensor fixes in one place permanently, it doesn't matter whether it is level or not so long as it is firmly mounted. you get your perfect level once, calibrate the sensor and that is it for as long as you keep the RV or caravan.

That item is not though so useful for a caravan, you are still faced (like a bubble level) with going round to actually look at the unit. The display on mine goes where ever you can easily see it, in a caravan you just hang the display in a front window, easily visible from outside. Mine is also much more accurate than anyone could possibly need. It will also just cost you a bit of time, to build it - how much better can it get?
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Unread 29th May 2015   #4
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I've revised the write up, with a component list and the display, with a much neater box.
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Unread 30th May 2015   #5
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Hi Well an excellent contribution to the forum and a great write up with pics that I am sure will generate some good discussion. Well done mate
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