Need some help with a small project please

[Luckymarkus]

Hi All ...

I need to make a small electronic device that measures a TPS (throttle position sensor) and displays it on a 3 digit display in 0 to 100 percentage format. The TPS units have 3 wires ... earth, 5volt and output.
At lowest position it outputs something like .6volt and highest position outputs up to the full 5volts. It would need to have some sort of potentiometer adjusters for both the low and high range so the unit could be calibrated for different TPS units. Hopefully it could be powered by the 5volt supply but it could be powered by say a DC12V adaptor.

I understand what I need, but I lack the raw electronics knowledge to work this out ... I have soldering skills and could make it if I has a schematic of sorts that a nube could understand, and a list of components I would need ...thanks in advance

cheers Lucky

 

[MikeMl]

Do you have a 1.999Vdc full-scale panel meter that does not require an isolated power supply to run the meter (most EBay cheap ones have that restriction)?

If so, I can supply you a circuit that puts out 0-1.00V while the input goes from xV to yV, where x is ~0.6v and y is ~5V, where the offset and gain are adjustable so the meter reads 0.00 to 1.00.

 

[dr pepper]

As mike says, but a 10k trim pot might be a simpler idea, might not be perfect but it'd be a start.
If the vehcile allready has a obd connection you can get obd to blutooth converters cheap and you could display throttle position and a load of other stuff from the engine on your mobile.

 

[Luckymarkus]

that sounds awesome Mike .... I am trying to find the correct panel meter but not having much luck

 

[Luckymarkus]

could this be made to work with an extra power supply to run the display? **broken link removed**

 

[cowboybob]

Welcome to ETO, Luckymarkus!

could this be made to work with an extra power supply to run the display? **broken link removed**

Max voltage range (100VDC) of this device would disallow lower TPS signal levels (0 - 5VDC) accuracy.

This would suit your purposes better: **broken link removed**
(5VDC power supply need can be easily achieved with a 7905 regulator)

Might be a cheaper, similar device out there somewhere.

You could simply display the raw TPS value (o.6 - 5.0VDC) with (it appears) 4 decimal place accuracy. Don't know if the TPS signal is linear or not. Anything more sophisticated (say, as a linear percentage, 0 - 100%) will require additional circuitry, up to and including a microprocessor.

 

[MikeMl]

**broken link removed**with reduced accuracy, but no separate regulator required.

 

[cowboybob]

**broken link removed**with reduced accuracy, but no separate regulator required.

Yes, better...

 

[Luckymarkus]

I believe the signal is linear Cowboybob I need to display the 0 - 100value so that i can tune the motorcycle accurately. trying to find values in percentages the same as my tuning tools would be a nightmare ... not what was %60 of 3.76 volts

 

[cowboybob]

Here's an analog OpAmp circuit for converting the output of the TPS to a 0-1.00 VDC signal, emulating a 0-100% position. Note that it's currently showing a half-throttle (2.5VDC) TPS signal. The circuit is linear.

No doubt there's a simpler/better/more accurate analog circuit but it'll give you an idea of a way to accomplish your goal.

The DVM= value is what would be displayed (probably without the ".83" portion) by the little voltmeter MikeMI suggested.

If this concept doesn't suit, you'll have to go the digital (microprocessor) route.

 

[KeepItSimpleStupid]

This https://www.murata-ps.com/en/dms-eb2.html is an accessory to their line of panel meters. I have nothing but high praise for the company. I used on of their models so that mass flow controllers in the semiconductor industry would read in engineering units. I did something cute. I had a switch that placed 5V at the meter and then you adjusted a pot until you read the FS value. Set the decimal point and you were good to go.

Aside: There was one time I had to also calibrate stuff, but there were fixed output voltages of say 5V or 200 mV. I used a secondary number, initially 1.000 to tweek FS.
So, you set the nominal FS and the nominal output and then had tweek number. It was better than 0.956 V/milli-Torr or whatever. Not applicable here.

What would typically do, is divide the not quite 5V (span) to 100 mV (100 mV=100%) for display and set the decimal point accordingly and without loading the source appreciably. 200 mV is usually the "base range".

The TPS is typically ratiometric (my understanding), so you might want to consider that. It's not strictly 5V = 100%. It, whatever the power supply is makes it 100%,
So, if the supply is 5.1V, 100% is 5.1V

To make the meter ratio-metric, you would have to supply a likely buffered and divided new reference from the 5V source you are using.

Many times, the meter requires an isolated supply.

Right now, my head (migraine) isn't capable of figuring out what you actually need.

==

Quick favor. Can you measure the output voltage at 0% throttle and the actual power supply voltage at the TPS and at the ECM?

 

[cowboybob]

Thanks, KISS. I imagine the migraines are becoming (have been) rather tiresome... (to say the least). Hang in there, my friend.

Part of my thinking for this was that the throttle's position is never really at zero, else the engine wouldn't idle, and hence the 600mV low end figure. Although it is also my assumption that the bike is injected. Obviously, could be wrong, but can't see any other reason for there to be a TBS.

I also left out of the circuit any calibration pots which, of course, would be needed to tweak the calibration of the gains of both OpAmps.

... Quick favor. Can you measure the output voltage at 0% throttle and the actual power supply voltage at the TPS and at the ECM?

Luckymarcus, just carrying forward KISS's request: this info would be very useful.

 

[KeepItSimpleStupid]

CBB:
Remember that sensors typically can't go to zero because of the difficulty getting zero volts. It could just be a "diode drop" that's calibrated out, PLUS it gives you an "open sensor" detect.

So, while the sensor may be ratiometric, the offset(s) might be calibrated out. e.g. The zero offset is easy. The full scale is always the power supply voltage. The system voltage at the sensor and ECU should not be too different.

A reminder, the range of the offset can be restricted and a turns counting dial and 10 Turn Potentiometer put might be helpful, they are cheap from China,
The "right way" to do this might be to have an OBD tool, if available and see if the calculated values agree. e.g. the 50% point is going to either be between the offset and 5V (doubt it) or the offset and the ACTUAL 5V source value, ALTHOUGH it's possible that they use a 5V reference.

This **broken link removed** DPM is about $90.00 from mouser, but doesn't include the option board. Note the blurb about 5 V and 9V supplies and the measurement capabilities. 9V battery operation is also possible. The option board is $14.00. The connector may or may not be included.

You need to look at the application notes too. https://www.murata-ps.com/en/application-notes/digital-panel-meter-application-notes.html

CBB: the east coast storm (ice/rain event) that went through the east coast Saturday wasn't nice to my head.

 

[Luckymarkus]

i checked one bike today and zero TPS (yes injected and does idle at zero ) was 1.72vdc and 100% throttle was 4.74 vdc .... but i do know that this can be different for many different bikes ant TPS's .. that why i need a decent amount of adjustment to calibrate it to any bike i wish to use it on

 

[MikeMl]

i checked one bike today and zero TPS (yes injected and does idle at zero ) was 1.72vdc and 100% throttle was 4.74 vdc .... but i do know that this can be different for many different bikes ant TPS's .. that why i need a decent amount of adjustment to calibrate it to any bike i wish to use it on

Ok. Assuming that the TPS is like a potentiometer that has three connections: Top, Wiper, and Bottom, can you make connections to all three of its wires while it is still in the bike? Or do you want a test box that powers it off the bike?

If you measure the voltage on wire Top, Wiper, Bottom with respect to chassis ground, what are the three voltages?

I'm guessing that if the bike powers the TPS:
V(Top) = 5.00V?
V(Wiper) = 1.72 to 4.74V as the control is moved?
V(Bottom) = 0.00V?

With the bike power off, what is the resistance from V(Bottom) to the bike frame?

Do you have a source of 12Vdc (bike's battery) in addition to the three wires, above?

How much current can you steal off the 5.00V wire V(top)? Enough to power the DVM, or should it be powered off the 12V wire?

Please confirm.

You are willing to buy a 0 to 1.00 Vdc panel meter, right?

 

[KeepItSimpleStupid]

Mike:
Could be a rotary hall device.

The meter and ranging board I iinked too is a bit pricey, but looks like it could provide the facilities with a 5V supply.

Not sure if offset on that device is + only though.

Looks like a 0 to -2 offset is needed and a 3 to 5V FS adjustment range (referred to sensor unless they reference it to +- Vref.

Its generally a +-mV 200 V "movement".

So the resulting Span voltages computed from above need to be scaled.

A 1V meter probably already has a divider.

 

[KeepItSimpleStupid]

Hey. It looks like this https://www.newark.com/murata-power-solutions/dms-20pc-0-5-24rl-c/process-meter/dp/87K3641 will do EVERYTHING needed OFF THE SHELF/

Nothing special required, except I'd probably add a couple of components for transient protection, reverse polarity protection and a small fuse. There is still the case to consider and things like a power LED and how to connect to your system.

It COULD, however be inconvenient, but I doubt it would be too difficult to mount more rugged potentiometers on the front panel.

I suspect you would want panel mounted potentiometers and it's likely possible you can unsolder and use different ones.

10 Turn panel mount pots are common. If need be, you can probably make course and fine adjustments. 4 pots and dials will cost an arm and a leg unless you get them from ebay/China/aliexpress/

You won't know the value needed until you get the meter and you won't know if two pots in series will work until you get the meter. i.e If a 10K pot is used for gain, you could probably replace it with a 10K in seres with a 1K UNLESS all three terminals go to different places in the circuit. It's likely that two terminals are the same. i.e. CCW and wiper.

If stuff is about the same, you could use a fixed resistor and a potentiometer which could be useful for gain, e.g. 2 to 5 V.