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  • Author Author: mcb1
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Forget Me Not : LPG Level

mcb1

This post is not really for my challenge. but struck me as being another product looking to be hacked ....image

 

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LPG Level

While I was purchasing some products in a local electronics retailer, I spotted this.

http://www.jaycar.co.nz/productView.asp?ID=QM1662&CATID=97&form=CAT2&SUBCATID=946#1

 

image

 

 

I knew Inderpreet    was looking at measuring his LPG tank, and because this was so cheap, I had to buy it.

 

I've done nothing more than opened it and take the photos. (click on them for full size)

 

    imageimageimage

The unit takes AA batteries , and the metallic portion on the rear is magnetic.

 

A closer look inside

 

  imageimage

 

It appears to have a PIC 12F675 chip which drive the two ultrasonic transducers and then the LED's and speaker when the level is low.

Just what R6 does is anyone's guess.

 

I got curious so I put it on our Bottles.

Its not extremely loud (I wasn't able to simulate the drop in level), and the LED's only briefly flash.

 

It's designed for a BBQ rather than fixed cooking bottles, but could be modified to add a small RF device.

I'm also not sure what the local insect population would make of the new home, and I'm certain it wouldn't take long for something to take up residence.

 

 

They are distributed by Electus

Electus Distribution

 

 

Enough distractions back to me challenge.

 

 

Mark

Parents

  • Thanks for the teardown sir.

    I was not sure what kind of ultrasonic transducers were used but for the price they are worth it. There are fluid sensors in the element14 catalog but they are not cheap.

    The problem with this setup is that you cannot find out the rate at which the storage is being emptied as well as no projections can be made regarding when a refill will be needed. I'm testing the weight based system and I like the results.

     

    The only blunder I have made is using a single load cell. The better arrangement would have been three 20Kg Load Cells in a balanced tripod for a wieghing machine kind of system. I will be upgrading it once I am done with the current version.

     

    Many thanks again.

     

    Regards,

    IP

Comment

  • Thanks for the teardown sir.

    I was not sure what kind of ultrasonic transducers were used but for the price they are worth it. There are fluid sensors in the element14 catalog but they are not cheap.

    The problem with this setup is that you cannot find out the rate at which the storage is being emptied as well as no projections can be made regarding when a refill will be needed. I'm testing the weight based system and I like the results.

     

    The only blunder I have made is using a single load cell. The better arrangement would have been three 20Kg Load Cells in a balanced tripod for a wieghing machine kind of system. I will be upgrading it once I am done with the current version.

     

    Many thanks again.

     

    Regards,

    IP

Children
  • in reply to ipv1

      send me a PM and I'll send it to you.

     

    I agree they don't give you a rate.

    Has anyone opened one of those newer bathroom scales ...?

     

    Mark

  • in reply to mcb1

    I think the load cell I am using is the one from a digital weighing scale. I bought it from SeeedStudios.com. I also bought some from ali express . com but the problem is when and what. The worst delay was 3 months from order date and the what means no datasheets for the sensors purchased.

    image

    Finishing up as much as possible to meet deadline.

     

    Regards,

    IP

  • in reply to ipv1

    Inderpreet.

    I wonder if you were to make a hinged shelf to sit the bottle on, and at the hinge side at right angles, have the load cell where its being 'squashed'.

    You would loose a small amount due to the hinge, but that's easy to calibrate out.

    image

    It would solve having to use 3 cells in some form of balancing arrangement, and you could use mechanical advantage to either increase or decrease the load on the measuring cell.

     

     

    mark

  • in reply to mcb1

    Mark sir,

    That's a good idea. I tried something similar with a see saw arrangement  which is a type I lever arrangement. The equation would be

    Load x load arm length = sensed weight x sensor arm length

    Now the problem is when the lengths are small, the difference or error in placement Of the bottle will cause errors.

     

    Your suggestion is however very interesting and I just might give it a go. The problem I foresee is balancing a 30kg cylinder on a platform. I am not sure what design would work in wood since anything else will be much difficult.

     

    Thanks for the idea.

     

    Regards

    IP

  • in reply to ipv1

    Inderpreet.

    I'd use a piece of heavy angle aluminium or metal, as the right angle, which the load cell attaches to.

    Two simple heavy duty hinges would work as the pivot.

     

    You could add a 'locator' to ensure the bottle was in the correct place (piece with a large hole that the bottom sat it)

     

    In my mind this only need to be 100-200mm above the ground, and the arc between full and empty would be very small as the load cell doesn't really compress.

     

    Mark