Pressure sensors for reading psi.

White Wolf Mac

Hi my name is White Wolf Mac. Me and my friend Gargoyle is working on building a HHO cell, and we are going to use the BASIC Stamp to control the cell. In the event of a malfunction or the cell is in danger of damage the BASIC Stamp will automatically turn off the cell. The only problem is that one thing that we need the device to do is read the presser inside the cell. Does any one have any ideas of what we can do? All thaws that help will be able to buy a complete HHO kit at price of cost. I will send you a massage when we have completed the project and in that massage it will contain an ID code that will tail us that you have helped on this project. Thank you for tacking the time out and reading this massage.

pgamblin

Mechanically you could use some type of small relief valve similar to a radiator cap. You mention what the pressure range is, but the flexiforce sensor sold at the parallax site may be a viable option. It is, I believe, a linear sensor 0-100 lbs = 1 to 4 volts out.

SRLM

A simple option would be to use a switch and some sort of spring assembly. The easiest would be to get a tire guage that has the stick pop out when the pressure increases. Then you just add a momentary switch to the end, and allow it to press against something. This has the added benefit of letting you see the pressure for when you are there.

Alternatively, you could use a linear pot with the same sort of pressure movement device, and use a RCTIME command to measure the pressure. This gives the added benefit of letting your program know exactly how much pressure there is, rather than a single value.

If you just want something machanical, check out the model steam engine hobby. They are built with that sort of appliances.

Scurge

This may or may not help:

get a single action 9/16 bore pneumatic cylinder and pipe the line to be gauged into that. have the shaft press against the parallax pressure sensor mentioned above and the reading in lbs is lbs/in^2 as the area of the bore is about .993 in^2. i hope that will be accurate enough. If nothing else the use of the pneumatic cylinder would point u in the right direction. im sure there is a simpiler way to go about this though.

EDIT:
some single action cylinders have return springs and would need a little calibration to make them more accurate. I would put a tire valve stem in-line and calibrate it with a digital tire pressure gauge, this setup could allow you to have real-time pressure monitering. but if you dont need it all that fancy, the analog tire-gauge, micro-switch technique would work fine.

Post Edited (Scurge) : 8/7/2008 11:31:53 PM GMT

MSDTech

What pressure ranges are you looking at?
Freescale Semiconductor makes absolute pressure sensors, such as the MPXA6115C6U/C6T1 CASE 482A-01 that can be attached by a tube to the unit. You would need to use an ADC to convert the analog output to a digital reading.

jpyle

· You may be able to hack a digital "tire" guage and use the pressure sensor as it puts out an electronic value. I have not been into one yet, but I do know of this being done with good results on a stamp. Simplicity is your best bet here, I beleive.· SRLM's idea using a pencil type guage sounds like your best choice to me. There are several pressure ranges to choose from (garden tractor tire at·6 pounds to airplanes at hundreds of PSI)·with an adjustable switch and visual confirmation all in one.··JP

SRLM

Whatever your final choice in measuring guage is, be sure to add a mechanical relief valve. The Basic Stamp is very reliable, but it is a system that requires constant input (electricity) If that input is interruped, your electronic safety valve may not open. Then you would have a big mess of the cell all over, and possibly injury/death. So it is absolutely essential that you add a simple mechanical safety. As I mentioned before check out the model steam engine hobby: those guys really know alot about how to deal with pressure and make it safe.