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help me build a pressure transducer power pack

posted Apr 11, 2016 01:47:38 by tony redolfi
got some plans here for a 9volt power box with 5volt output but I'm a little confused about some of the parts I need to get.. here are the plans

so ill just list my questions

1. the 100 UF capacitor,, I see they come in all different volts as well,, would a 100UF / 10V work?

2. the 1K resistor,, what wattage do I need,,, 1/4watt 2watt?

3. what kind of diode do I need to install to protect the circuit.

that's about all the questions I have for now,, thanks guys

[Last edited Apr 11, 2016 01:50:07]
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12 replies
tony redolfi said Apr 11, 2016 02:21:08
update,, just talked to the guy who built this,, he said the 10v will be fine for the capacitor and 1/4 v for the resistor will be fine as it just powers the led.

the diode is Power Diode 1N4004 from Radio Shack.

its a really nice box, here is the video link of the unit he built

How to make a pressure transducer .

[Last edited Apr 11, 2016 02:21:59]
AndyMacFadyen said Apr 11, 2016 06:51:24
It is easier and cheaper to buy a complete swith mode voltage step down off eBay.
A tiny module called a UBEC used for stepping down battery voltage by drone builders is exactly what is required as it is designed to give an output free from voltage spikes.
In the UK these sell on eBay for around £3 which is about 5$ US or €4.
"Rust never sleeps"
tony redolfi said Apr 11, 2016 14:40:56
I know there are easier ways to do this, but I do like the look of a self contained box, I done ordered everything last night, all the different components it totaled up to around 17bucks.

I'm also adding a volt gauge to the box,, I found one for $1.30 so I can monitor the 9volt battery

the battery box is nice because it wont need leads going to the car battery,, so its less wires to hook up.

Ill post pictures of this build but that will be awhile,, to save money I ordered everything from overseas,, so ill be starting this build in a month or so from now.

AndyMacFadyen said Apr 11, 2016 16:22:22
A UBEC is really tiny the size of a rectangular postage stamp but the real adavantage is that output is almost completely spike and noise free.
"Rust never sleeps"
tony redolfi said Apr 11, 2016 18:26:20
I found this step down on ebay for a dollar,, I don't know if it would need a capacitor added to it, but its pretty small.

I done already ordered all the parts last night,, I was also thinking this morning that one could use the USB port on a laptop as those put out 5 volts too,,, anyway ill get to brush up on my circuit board soldering once all my parts get here hahaha

tony redolfi said May 06, 2016 19:43:28
ok I just got this built and tested,,, I was hoping you guys could take a look at these screenshots and let me know if you think this is showing enough detail, I hope this transducer has a fastest enough rate

of course I need to re watch all the videos again,, but I'm just glad I got something on the screen

I ended up building that circuit using a proto type circuit board and added a volt meter to keep an eye on the battery. banana jacks plug right into the unit

[Last edited May 06, 2016 19:51:28]
AndyMacFadyen said May 07, 2016 05:15:38
Most of the mush is down to the limmitations of the Hantek 1008 it has no built in filtering and there is no control over the aquisition mode and sampling setup so can have problems with rapidly changing signals.
More expensive scopes usually have the signal aquisition mode configurable for peak or averging and have built-in high and low pass digital filtering.
You could try making up a simple external Low Pass Analogue Filter to go between the sensor output and the scope. A low pass filter cuts off the higher frequencies cleaning up the signal.
The RC type really simple to make however it distorts the signal particularly where there is a step change as in a square wave.

The capture below is using my Owon SDS7120v using its' built-in digital low pass filter.
I pobably over filtered it by choosing too low a cut-off frequency as some of the detail of the turbulence on the exhaust stroke is missing.

[Last edited May 07, 2016 05:59:49]
"Rust never sleeps"
tony redolfi said May 07, 2016 14:08:41

ok,, that makes sense, I started reading those links, I understand how to build it, not sure what parts to buy as I know nothing about hertz as of this second. basically I have no understanding of what range I'm operating at and what I want my cutoff frequency to be

do I have a hertz measuring window on hantek? ill go see if I can find that,,, I'm also going to hook this unit back up and mess with setting a bit more.

this is a lot of stuff to figure out and learn,, bare with with haha

ok ill be back with a betting understanding after doing some more reading
AndyMacFadyen said May 07, 2016 18:52:43
You can use household chocolate block connector to build a simple filter without soldering that way you can experiment with different component values. Try starting with200 ohms and 0.22 uF
"Rust never sleeps"
tony redolfi said May 07, 2016 21:43:58
hey thanks man,,

just got back from playing around with it again,, i changed it too all different types of settings, take a look at these new shots,, a lot clearer,, but not much detail

ill go order some parts for that filter,,, i been using this breadboard thing i picked up to asemble components without solder,, it works really well, got it off ebay

what type of wattage do i need for the 200ohms resistor? and what voltage for the capacitor? sorry to ask,, i feel like some sort of electronics butcher!!

AndyMacFadyen said May 08, 2016 06:13:41
That looks OK, a cranking compression test always looks very different from a running test.
If you look at figure 6a and 6b on this page on you will see a nice example of a normal cranking in-cylinder cranking test. Also here on the Pico website

With the cranking in-cylinder test the heights and shapes of the compression peaks are the primary area of interest the running compression test is better for picking out detail
Minimising the air volume in the hose connecting the sensor to the cylinder and using as stiff a hose as possible helps avoid loss of detail.compente

For components I just buy a selection bag of assorted capacitors and resistors from Maplin which is our equivalent of Radio Shack. Wattage and voltage rating don't matter much.
[Last edited May 08, 2016 12:50:55]
"Rust never sleeps"
tony redolfi said May 08, 2016 13:50:21
wow,, so it looks like this tool is working perfect, thanks for all the help, I would have had this done sooner but I wont buy my parts local, I get everything from china and it always takes about 3 to 4 weeks to get my parts.

they just want way too much money for parts here, around 3 to 4 times what I can get the same part in china for.

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