KISS Pitot bench design

[Tony]

Nick, here is a data sheet for the MXP5010:



Note that it MUST be powered from a five volt accurately regulated supply. A nine volt battery is not acceptable. Surprisingly there is no mention of maximum permissible operating voltage in the specification sheet, and it is entirely possible that 9v may have killed the chip.

It would also be a very good idea to fit all the external decoupling capacitors that they recommend.

[Nick]

I used ta 9v because they showed a circuit using a 9v with a 7805 regulator On the Freescale site with a similar sensor. So the sensor never saw 9v only 5v. I did notice looking trough the app notes that there are some of those that only use 3 pins, (5v in, v out, and ground). This one I have has 6 pins that are used. (vout, VCC, G, V1, V2 Vex) I'm still not sure how to make it work, it's on the back burner until I have time to do more research. I have an extra that has not Been touched, in case I did fry it.



Nick

[blown928]

New pics of the KISS bench....



I've added a baffle around the exhaust flow tube so the motors aren't blowing directly on it


The top showing the suck hole on the left and the blow hole on the right, the 2 valves for the flow elements at the back, and the red control box.




Close up of the exhaust valve and the control box.



My first victim. Note the cover plates on the blow & suck holes. This lets me compare the intake flow element readings to the exhause flow element readings for leakage testing.

[Tony]

That is looking remarkably like my bench !

One thing I did was screw some bolts from inside the steel angle frame so the treaded ends project outward (like studs). The front cover panels are much easier and faster to replace, and there is no danger of crossing a thread and damaging the rather shallow threads in the angle frame.

That looks excellent, and I bet you have absolutely zero air leakage.

[blown928]

Right now I have some leakage around the valves. I assembled them without any silicone, thought the rubber seals would be enough but they weren't. I have to diasssemble and goop them up.

Tonight I'm hoping to do that and get the electronics installed so I can do a proper leak test. I expect the leakage to be very small, but we'll see.

[blown928]

Started up the bench with a manometer for the first time this afternoon. The digital stuff's not hooked up yet, I made a 48" vertical water-based manometer. I could pull 44" wc through one of my Porsche 928 intake ports with 4 of the 16-1234 motors. 3 motors on full and the one variable at about 1/2 let me dial in 28". I don't have the inclined manometer on the flow element yet so I don't know cfm.

A few initial thoughts:

Looks like 4 motors will be sufficient for now.

The router speed control works pretty well, I can dial in any depression I want up to the max the motors will pull. I need to wait a few seconds for the manometer to stabilize after an adjustment though.

I'm going to need stronger springs. I used springs from a TP roll holder ($0.97 at Wall Mart) and the valves just pulled open when I kicked on the second motor.

The sound insulation I added may have been worthless. It was pretty quiet until I mounted the head, then it got REAL loud sucking in through the intake. I'm going to need some ear protection.

The fun starts now

[blown928]

Here's a pic of my head fixture, made from pine and 4"pvc pipe.