pressure sensor selection

[cdnrookie]

Hey guys,

Im looking for an inexpensive pressure sensor (yeah, I know im opening a can of worms with that sentence, lol)

Its for a home project, basically I want to hit the sensor and have it send a signal back to a micrologix 1000.

Nothing fancy, dont need to know how hard I hit it, just sense the impact. Ive gone through digikey and a handful of other sites but its over whelming the number of options available,

Any thoughts?

 

[nonuke]

Analog or digital?

 

[ndzied1]

When you say pressure sensor most think of air pressure or hydraulic pressure. What do you mean by "hit/impact" are you talking about slapping something with your hand?, a cylinder?

For a school projects with my daughter once I took a piezeo disk and mounted it to a board. Built a circuit shamelessly lifted from the internet that fed into an arduino and it could detect someone knocking on the board...

 

[nonuke]

This is a digital Pressure Sensor.

 

[cdnrookie]

Thats kinda what im looking for, I guess its more of a force sensor im looking for

 

[cdnrookie]

nonuke - thats too funny!!!!

 

[osmanmom]

http://www.aliexpress.com/cheap/cheap-knock-sensor.html

 

[ndzied1]

Looks like what you need then is a pushbutton.

 

[jethridge]

We use the GP-50, 311 series for most applications. It's 4-20mA out, 0-15K PSI, not sure if it'll be in the right price range though.

 

[RDS]

Something along these lines?? http://www.instructables.com/id/Use-a-DIY-Pressure-Plate-Switch-to-Automate-Your-H/

 

[TConnolly]

You can get load cells off of ebay that are geared toward Arduino hobby enthusiasts for prices as low as a couple of bucks each. You'll need an amplifier, but you can find simple amplifier circuits online. I suggest a Google search on arduino load cell.

 

[OkiePC]

We used something similar to this:

http://www.gatedepot.com/product/miller-edge-ps20-switch/

on powered sliding doors in a refrigerated plant. It is designed to be attached to a soft thin walled rubber hose which gets routed through the weather stripping on the edge of a powered door or gate.

The pressure switch activates on a very low pressure. The way ours were wired, if the door hits a person or a forklift, the switch breaks the motor circuit and kicks it into reverse. You could wire it up to behave however you want, and they can be pretty darn sensitive.

 

[ndzied1]

We used something similar to this:

http://www.gatedepot.com/product/miller-edge-ps20-switch/

on powered sliding doors in a refrigerated plant. It is designed to be attached to a soft thin walled rubber hose which gets routed through the weather stripping on the edge of a powered door or gate.

The pressure switch activates on a very low pressure. The way ours were wired, if the door hits a person or a forklift, the switch breaks the motor circuit and kicks it into reverse. You could wire it up to behave however you want, and they can be pretty darn sensitive.

I started my career at a company that made doors for mass transit vehicles. A large part of every specification had to do with the door edges and how they would sense someone in the closing doors and reverse.

We once did a job where we partnered with a company in Austria that also made mass transit doors. We asked their engineers what they used for "sensitive edges" on the doors. They didn't understand and after we explained to them what we were talking about they said, "Why would anyone stand in the doorway when the doors are closing?"

 

[OkiePC]

They didn't understand and after we explained to them what we were talking about they said, "Why would anyone stand in the doorway when the doors are closing?"

At the plant in which I worked, our SAFETY director did that while demonstrating how to test the door edge switches to the safety committee.

He did not stick his arm out there or slap it, like a normal person would. Keep in mind these things do fail and that is what he is looking for. . .

He picked a door that rarely gets used which leads into a -40F freezer and sure enough, the hose was bad or the switch had failed. So this joker not only steps in front of it, he picks a spot right up against the frame where it is almost closed and it pinned him.

Luckily, one of the maintenance guys stopped laughing long enough to open the disconnect and push the door off him.

Only injuries were to his ego and reputation. The doors were heavy, but didn't move real fast, and motors and gearing were set up so they'd stall and overload before crushing him.

 

[ndzied1]

He picked a door that rarely gets used which leads into a -40F freezer

CTA found that pneumatic type sensing failed well above -40 (which was their spec). We resurrected an old design for them that consisted of a two long springs, one inside the other that fit inside the leading edge of the rubber door bumper. Deflecting the door edge would make the outer spring contact the inner spring completing a sensing circuit. The springs were silver plated.

I once found a conductive rubber I played around with to see if I could turn that into a switch but I left that company before I got anywhere with it.