Motorcycle air system pressure display


I’m new to this and have more questions than I have answers :).

What I’m trying to do is make an Air Pressure monitor/readout. I know what I want to do however I don’t know what I need to do it. I’m guessing some sort of microcontroller, code to translate voltage to PSI, and power. This will be on a 12v system however I step that down as I will on the “transducer” below.

  1. 0.36" 7-Segment Red LED Display 3 Digit - 0.36" 22.5147.2mm - similar to this:
  2. 0-100 psi Stainless Steel Pressure Transducer Sender For Oil Fuel Air Water - Operating Voltage : 5.0 VDC, Output Voltage: 0.5-4.5 VDC, Operating current: ?10 mA, Working pressure range?mPa??0-100 psi, Max Pressure? 150 psi, Burst Pressure? 200 psi, Measurement accuracy? ±2.0 %FSO, Temperature range of the error? ±3.0 %FSO, Response Time? ? 2.0 ms - just like this:

I have a very limited mounting area; the space will allow 34x20x30mm.

Any help/assistance is appreciated - I’d love a plug-n-play module but I haven’t found one small enough - also, I would like to keep this budget minded.

Thanks, Mac…

I don't actually see any question in your post - unless you are asking for someone to design the project for you?

If you want to develop it yourself it would help to know your existing level of experience.

If you have no prior experience of an Arduino I think you should get an Uno and work through several of the examples that come with the Arduino IDE - the PC program on which you develop Arduino code. You can, of course, download and study the Arduino IDE without buying an Arduino board - ypu just won't be able to test any programs you write.


This project would be childs play for anyone with a bit of programming knowledge and an arduino (of any flavour). Just get your hands on an arduino, download the IDE and start playing. You'll likely get hooked and start developing much more.

Thanks for the replies. I have no experience with this however I do have some programming in my background. My questions are really around:

  1. what Arduino board do I need?
  2. would the “nano” work for this?
  3. is there a board smaller than the “nano”?
  4. do I need other components?
  5. would a display like I attached “0.36” 7-Segment Red LED Display 3 Digit " work with an Arduino board?

Thanks for bearing with me on this, Mac…

For a simple task like this one I'd suggest an attiny chip. It's basically an arduino without the breakouts. So it's just a single ic with most the functionality, BUT you'd also want an arduino to do your development and to program the attiny chip. This approach also means that, once you've implemented your project on the attiny, you then have your arduino available again to move onto your next project.

Do a search on youtube for shrinkifying arduino projects.

For a simple task like this one I'd suggest an attiny chip.

I'm a fan of ATtinies myself, but that 3-digit 7-segment LED is going to need a lot of pins to drive it. An ATtiny84 might have just enough pins though.

An Arduino Nano or Micro is convenient because they have the USB-serial interface on board. An Arduino Pro Mini is a bit smaller, but requires the separate purchase of a USB-TTL serial adapter cable for programming.

Thanks again for the replies. Another thought, is there someone out there I could pay to build this item for me?

Again, Thanks....

Try here:

What area do you live in?

I'm in north Texas, just north of Dallas.

Aw that’s a shame, I’m in Essex (south east England) A tad impractical.

BTW What are you going to measure with this, (vaccum in inlet manifold?)

:), I want to measure the air pressure in my motorcycle air suspension system. There are units out there however my problem is where and how I want to mount it - it’s a very tight space allowing for a maximum unit size of 34x20x30mm (WxHxD). I attached a couple of pictures of the space with a 0.36" 7-Segment Red LED Display 3 Digit DVM so you can see.

I could hook up what I have but the DVM only shows the linear voltage output. 0 psi outputs 0.5V, 50 psi outputs 2.5V, 100 psi outputs 4.5V. - I’d really like to PSI

Thanks and let me know your thoughts, Mac…

That's cake. An ATtiny84 in the through-hole package is only 20mm long. Assuming you never need the decimal point on the display, only 10 pins should be required to multiplex it, leaving exactly 1 pin left over to analogRead() your sensor.

Circuit won't be complex, should be able to solder it up on a chunk of perfboard with a handful of components and fit within the space required no sweat.

Aw that's another shame, I was going to suggest you pay for all the parts (x2 so I keep 1 for myself as payment) and I'll build it over here then I could post you the working finished item.

Unfortunately my bike (A Yamaha Diversion 600) doesn't have such a sophisticated suspension setup. I take it you have a Harley?

Hey Ken, I do have a Harley, I also have something from your part of the world.... a '69 Triumph Tiger 500 that I have bobbed - 4" stretched hard-tail and a bunch of one-off parts - garage built. I built it for the Diablo Run through Baja. You know, air systems aren't just for Harley's; I put them on all sorts of metrics from Cruisers to Hayabusa's - I do a lot of tinkering. On the Busa a kid in the neighborhood wanted a trick air system so I did the front and rear, modified some air cartridges for up front and used a C02 bottle for the tank - instant up and down :).

This isn't for me though - I'm building a Trike for a Disabled Vet, he lost both legs below the knees. With his mobility issues I figured an on-board compressor would save him a lot of trouble. I've been fortunate and most of the parts have been donated, I picked up a salvage RoadKing for $4300 and when it's done I'll leave it outside his house with a note and the title - no cost to him as he's already paid enough.

BTW, if you built them for me you could still use one - maybe not for air pressure but pressure is pressure - you could use it for monitoring your oil pressure....

Thanks, Mac...

I admire your style. For such a worthy cause I'd be more than happy to chip in with any assistance I can offer. One suggestion I would make is that your choice of display makes things a tad awkward. Every segment of Every display needs it's own feed from the controller (which is a lot of control pins being used).

Now if you were to use a slightly different display, you could have an "I2C" connection to update it. This would have a few benefits. Firstly it would be able to be mounted remotely from the control circuitry. (it only needs 2 signal wires and another pair to supply power) You could also get a display that has far more characters (2 lines of 16 characters is typical).

Now with your microcontroller and display in place. You could then add other features for it, as and when, you feel interested. Fitting a simple push button on the handlebar would allow you to cycle through the different items to display. So besides Rear suspension pressure:

With the addition of a hall effect transistor on the forks and a magnet attached to a spoke on the wheel you would have a backup speedometer. Using this you could also have a trip meter.

with a simple sensor in the fuel line you could then have a Miles per Gallon meter (or whatever units of measure you want)

With a simple piece of wire wrapped around a spark plug lead (and a bit of jiggery pokery) you can create a sensor to display RPM.

You could buy a handful of temperature sensors (very cheap) and get readouts for temperatures of the engine, brakes, ambient air etc..

You could even go the whole hog and add a gps and gsm module. This way, if it was ever stolen, you could send a text message to it on your mobile phone and it will answer with it's location.

But anyhow, I'm getting ahead of myself. If this is a charitable gesture on your part, You may not want to build in this scalability.

Fist let me say that is extremely generous! I'm not married to the display and love the remote mounting option which alleviates some of the size limitations however I do have the size constraints with the display placement (see previous attached photos) - what display would you recommend?

I see the value in the expandability, for example right off I would get 2 other sensors; 1) another pressure transducer for oil pressure, and 2) a temperature sensor for oil temp.

The housing in the pictures has 3 bays, 1 for the display and 1 for the air control switch - leaving 1 bay open which (if needed) would allow me to mount up to 2 switches , one of which could be the toggle switch to scroll with.

Curious, would I be able to power the display and micro controller with 12v or would I need to step the 12v down?

For this 1 I think a "locked down" module would be best however even though I don't have an air system on mine I would mind a second unit - I could use the oil pressure and temp and who knows maybe down the road I might put air on mine and then I'd be ready.

Thoughts, Mac...

Supply Voltage
Yes you'd want to provide a source of 5v but That should be easy enough. A standard 12v to USB charger should do the job nicely.

I'm a little concerned about the sensor you have linked to. It is incredibly cheap and I can't find a datasheet for it anywhere online. I assume that it works on the same principle as the more expensive jobbies. (ie output voltage/supply = Actual pressure / FSD) At that price i'd be inclined to snap it up and assume it's going to work this way. (there may some calibration to get it to give the results we expect)

This is the kind of thing that I had in mind. The dinky board on the back is the I2C interface. I have one of these and have been quite happy with the display but it does occur to me that I've never seen it out in bright sunshine so I'm not too sure how readable it would be. It has a pretty bright backlight so I think it would be fine. The contrast is adjustable through a potentiometer on the board. (my one doesn't have the i2c interface but the display itself is identical) My gut instinct tells me that it would be fine. But I'd rather take it outside in the morning to see just how readable it is. (it's the dead of night here at the moment). The size of this display is:
width just under Three and a half inches.
Height just over one and a quarter inches
Thickness about Three quarters of an inch.

I'm curious as to where that box (with the 3 bays) sits on the bike.

... in bright sunshine ... It has a pretty bright backlight so I think it would be fine.

Actually, in sunlight, a standard black-foreground-silver-background LCD display needs no backlight at all. Such displays are at their most readable in direct sunlight, and only need the backlight in low-light conditions.


... in bright sunshine ... It has a pretty bright backlight so I think it would be fine.

Actually, in sunlight, a standard black-foreground-silver-background LCD display needs no backlight at all. Such displays are at their most readable in direct sunlight, and only need the backlight in low-light conditions.

Good point.