DIY Pressure Transducer

Built my own kit with 100 and 300 psi transducer. To test the 100 psi I set the compressor air to 50 psi. With the rubber tip nozzle I pressed it against the sensor and hit the trigger. it read 49.8 psi. Next was the 300 psi doing a in cylinder running compression on a 2014 Elantra. I noticed on the capture that on the exhaust stroke its not quite on 0 psi as I've seen on other captures from online. I customize my probe 0v = -37.5 psi, 0.1 = 0 psi and 4.5v = 300 psi. Maybe the settings need to be tweaked more? You guys can chime in. Last but not least bought the storage box from Harbor Freight with a their 25% off coupon. Happy Easter everyone.

Very cool, nice work

Where did you get the transducers from?

From eBay

Charles Acosta wrote: From eBay

Do you have a link? I purchased a 300 psi transducer from ebay awhile ago and it didn't work as expected.

[ebayhttps://www.ebay.com/itm/USA-New-Pressure-Transducer-or-Sender-Stainless-Steel-for-oil-fuel-air-water/253238407682?ssPageName=STRK%3AMEBIDX%3AIT&var=552357600573&_trksid=p2060353.m1438.l2649

No eBay APP ID and/or Cert ID defined in Kunena configuration

Charles Acosta wrote: [ebayhttps://www.ebay.com/itm/USA-New-Pressure-Transducer-or-Sender-Stainless-Steel-for-oil-fuel-air-water/253238407682?ssPageName=STRK%3AMEBIDX%3AIT&var=552357600573&_trksid=p2060353.m1438.l2649

Your link didn't work, I fixed it though, Thanks!!

Nicely done, it is a really good feeling when you get your successful in-cylinder waveform with a home build sensor.

No eBay APP ID and/or Cert ID defined in Kunena configuration

Ro-longo wrote:

Charles Acosta wrote: [ebayhttps://www.ebay.com/itm/USA-New-Pressure-Transducer-or-Sender-Stainless-Steel-for-oil-fuel-air-water/253238407682?ssPageName=STRK%3AMEBIDX%3AIT&var=552357600573&_trksid=p2060353.m1438.l2649

Your link didn't work, I fixed it though, Thanks!!

You welcome

Missed this one
I'm impressed. Nice work and a LOT cheaper than a WPS500

I just built my own transducer also, but took a slightly different approach. I used a Drok 2203 buck converter which takes between 22-8vdc input and outputs steady 5vdc. I could just carry around a 9v battery and connect it, but I'm cheap so I want to just use the car battery as my power source.

The problem I've run into is that AC from the alternator is being passed through and making my waveforms hard to read:



So I was thinking about taking a 0.1uF capacitor and hooking it across the transducer signal wire and ground to shunt the AC component to ground and clean up the signal, but I'm no electronics engineer and was wondering if someone here might know if that'll work.

By the way, here are some nice online transducer training materials:

Just scroll down to the middle of the page:

www.picoauto.com/library/training

Example captures of various types of problems:

www.automotivetestsolutions.com/pressure...en-shots-page-1.html

You may have to go the 9 volt battery route to see if you get a cleaner signal. If you do buy a pack of 9 volt batteries.

After some testing, I discovered that it is the transducer itself generating that 40mv, 1 kHz sine wave noise:



I might try the transducer the OP bought and see if I have better luck.

After experimenting with various capacitor sizes I have laying around, I found the best results came from a 0.1uF mylar cap between the signal wire and 0V ref. It reduced the amplitude of the sine wave by almost 50%. Couldn't get anything better than that. However, I think the real problem is just that these transducers are cheap Chinese junk.

SailorBob wrote: After experimenting with various capacitor sizes I have laying around, I found the best results came from a 0.1uF mylar cap between the signal wire and 0V ref. It reduced the amplitude of the sine wave by almost 50%. Couldn't get anything better than that. However, I think the real problem is just that these transducers are cheap Chinese junk.

Use the link I posted earlier. They cost me 20 bucks and it turned out well. With the Pico it zeroes nicely.

It also works with the Verus but it is not zeroed. You could still do the numbers

No eBay APP ID and/or Cert ID defined in Kunena configurationIt turns out that there were two problems. The buck converter was generating a 400 kHz 40mv sine wave on it's power output, and the transducer itself was also generating a bunch of noise. I was able to clean up the converters output with an RC low pass filter I made from a 47 ohms resistor and a 1uF cap.

As far as getting a new transducer, the one you used doesn't ship to Israel, but I found this other one that looks pretty good, I'm getting a -14.5-30 psi and 300 psi.



If you're interested in the LFP, you can see more about it here:

electronics.stackexchange.com/q/370804/149212

not sure why the ebay link isn't showing up....

here's the final fix. I was able to clean up the signal on the 200 psi transducer enough that it's useful for work:

SailorBob wrote: here's the final fix. I was able to clean up the signal on the 200 psi transducer enough that it's useful for work:

Can you do a cranking or running waveform?