Textile pneumatics, now with pressure feedback


An ongoing project with the ever-marvellous Rusty Squid.

Following on from my initial experiments, I wanted to try using pressure feedback with these heat-sealed textile pneumatics.

I got a couple of pressure sensors, and put this rig together:

The complete parts list is:
"DC 6V small air pump Micro Pressure Pumps Oxygen pump sphygmomanometer UK"
"DC 6V NO Micro Straight-through Air Pressure Relief Solenoid Valve FA0520F"
"Pressure Gauge 50mm 63mm 100mm Dial Bottom & Back Connection Pneumatic Air Range" (0-1 bar, 1/8BSP)
"TEFEN Nylon Pipe Fitting Plastic Barbed Hosetail Joiner Tubing Connector Blue" (Female swivel nut, 1/8 BSPT by 5mm)
"Tee Male, Push-On, POM"
"ABPMANN004BGAA5, Piezoresistive Pressure Sensor 4bar 6-Pin SMT" (these are surface-mount only because I couldn't find through-hole ones in stock, so I had to solder them to header strip)(I only need 0.5bar for these pumps, the 4bar ones give me overhead for future experiments)
ULN2803AN octal Darlington driver
And a trusty Arduino Nano.

I wrote some simple code to give each compartment pressure feedback, which will either run a pump or open a valve in order to maintain each compartment at target pressure.


And I made a new device to try it with, which I hoped would have more of a range of movement than the last one

As you can see, it doesn't. Althought the two compartments are inflated alternately, with the pressure varying roughly sinusoidally, there's not enough stiffness in the spine of the thing to stop it just crumpling up.

Stiffness is improved by adding a stiffening rib of gluegun to each side (thanks, Tiff!), but the outer chamber still wants to curl up sideways.

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