Thinking on creating a digital cluster gauge
02-14-22, 02:49 PM
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Thinking on creating a digital cluster gauge
Hi all.
I'm thinking on creating a digital cluster using TFT screens and some microcontrollers. The thing here is that I have no clue on how all different signals that arrive to the cluster are generated. I mean, I assume oil pressure, coolant temp, and fuel level should be some kind of analog signal between X and Y volts. For all different signals (brake, ABS, etc...) I assume is just a binary signal, 0 for indicator OFF and X for indicator ON.
But what about RPMs and tachometer? Any documentation related to this?
Best regards.
I'm thinking on creating a digital cluster using TFT screens and some microcontrollers. The thing here is that I have no clue on how all different signals that arrive to the cluster are generated. I mean, I assume oil pressure, coolant temp, and fuel level should be some kind of analog signal between X and Y volts. For all different signals (brake, ABS, etc...) I assume is just a binary signal, 0 for indicator OFF and X for indicator ON.
But what about RPMs and tachometer? Any documentation related to this?
Best regards.
Last edited by GasGasJDM; 02-14-22 at 03:31 PM.
02-14-22, 03:36 PM
#2
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The FSM has just about everything you're looking for. It will require quite a bit of research into the Manual. Here's just a taste of what it'll take... from my own research...
Spic Racer GT40R - Interior simplified: Aim dash ++
Spic Racer GT40R - Interior simplified: Aim dash ++
Last edited by Carlos Iglesias; 02-14-22 at 03:42 PM. Reason: ADD
02-14-22, 03:51 PM
#3
RX-7 Bad Ass
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You're in for an uphill battle. You might be worlds ahead going to an aftermarket ECU that supports a plug-in digital dash like Haltech.
Speedometers read in pulses. RPM is voltage I think. Oil pressure, fuel level, coolant temp is resistance. Idiot lights are circuits either going to ground or 12v.
To pull this off you'd need a deep knowledge of automotive 12v electronics, digital to analog conversion, microcontroller design and programming.....it's a big ask. Or just plug stuff in with a Haltech and make it work.
Or, just use the stock cluster that works just fine.
Dale
Speedometers read in pulses. RPM is voltage I think. Oil pressure, fuel level, coolant temp is resistance. Idiot lights are circuits either going to ground or 12v.
To pull this off you'd need a deep knowledge of automotive 12v electronics, digital to analog conversion, microcontroller design and programming.....it's a big ask. Or just plug stuff in with a Haltech and make it work.
Or, just use the stock cluster that works just fine.
Dale
02-14-22, 04:18 PM
#4
Hi all.
I'm thinking on creating a digital cluster using TFT screens and some microcontrollers. The thing here is that I have no clue on how all different signals that arrive to the cluster are generated. I mean, I assume oil pressure, coolant temp, and fuel level should be some kind of analog signal between X and Y volts. For all different signals (brake, ABS, etc...) I assume is just a binary signal, 0 for indicator OFF and X for indicator ON.
But what about RPMs and tachometer? Any documentation related to this?
Best regards.
I'm thinking on creating a digital cluster using TFT screens and some microcontrollers. The thing here is that I have no clue on how all different signals that arrive to the cluster are generated. I mean, I assume oil pressure, coolant temp, and fuel level should be some kind of analog signal between X and Y volts. For all different signals (brake, ABS, etc...) I assume is just a binary signal, 0 for indicator OFF and X for indicator ON.
But what about RPMs and tachometer? Any documentation related to this?
Best regards.
Looks like he's pretty far along at doing exactly what you're looking at doing, big exception being he appears to be designing his display to work with CAN bus, so it's better suited to aftermarket ECU's. Once you deep dive into the FD's FSM/wiring diagrams you'll soon see that the stock dash inputs consist of a gaggle of discrete analog & digital/switch inputs feeding instruments.
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Akagis_white_comet (02-14-22)
02-14-22, 08:49 PM
#5
In 2012, I built a simulator box that generated every signal a RX-7 cluster would receive. Fuel, Temperature, Oil Pressure are all Resistance meters, referenced to ground, while the Boost gauge is a 5v Voltage Divider (0-5v range). Speedo and Tach are 12v pulses, so I used an Arduino and suitable code with a keypad. Just input the frequency desired, press a button and see the gauge go to the corresponding reading. Per Granny's Speed Shop, 120hz signal on the Tach signal pin makes it read 3600rpm.
https://grannys.tripod.com/rx7tachrecal.html
As for the FC and earlier speedometers, I just used an extra speedometer cable with a household drill, using a Dimmer Switch to control the speed. The drill I used had a maximum speed of 3000rpm, so I calibrated the Dimmer switch by going up from 0 until the Speedometer hit 60mph (1024 rpm, close enough to 1000) and marked the Dimmer Switch's cover plate with "33%" to match.
If you REALLY want to build a digital cluster, similar to what was optional in a Z31 300zx, C4 Corvette, etc, I'd suggest starting with an Arduino. The Oil Pressure, Fuel Level and Temperature senders can be biased with resistors and then given 5v so they behave as a Voltage Divider, like the Map and TPS sensors do. The resistor needs to be as close to the MIDDLE of the sender's range in order to behave correctly.
The Arduino natively understands 0-5v signals, so doing this turns them into a 0-1023 memory value that you can program the Arduino to do something with, such as moving a stepper motor, turn on a light, sweep over a LED bar graph, etc.
Here's an over-simplified example of what your desired code will basically do, using 10 LEDs for your intended display:
Read Pin 13 "Oil Pressure"
If Value =0~100, Write Pin 14 High (0-10 psi, Pin 14 has 5v)
If Value=101~200, Write Pin 15 High (10-20psi, Pin 15 has 5v)
If Value=201~300, Write Pin 16 High (20-30psi, Pin 16 has 5v)
and so on until you get to Value 1023 which is the LOWEST resistance the sender normally outputs (arduino sees 5v for this). Usually represents maximum oil pressure, max fuel, crazy stupid overheated engine, you get the idea.
You can see an example of the concept in action here, using a potentiometer to simulate the sender's signal:
https://create.arduino.cc/projecthub...r-graph-7e6212
Values may need to be tweaked to suit your senders' individual ranges, the real magic is all in the code. The above link includes an example of the code they used for it. Adjust the values to suit your needs and you'll be halfway there. Aaron Cake goes much further into Arduinos and cluster mods on his 1976 Cosmo here:
https://grannys.tripod.com/rx7tachrecal.html
As for the FC and earlier speedometers, I just used an extra speedometer cable with a household drill, using a Dimmer Switch to control the speed. The drill I used had a maximum speed of 3000rpm, so I calibrated the Dimmer switch by going up from 0 until the Speedometer hit 60mph (1024 rpm, close enough to 1000) and marked the Dimmer Switch's cover plate with "33%" to match.
If you REALLY want to build a digital cluster, similar to what was optional in a Z31 300zx, C4 Corvette, etc, I'd suggest starting with an Arduino. The Oil Pressure, Fuel Level and Temperature senders can be biased with resistors and then given 5v so they behave as a Voltage Divider, like the Map and TPS sensors do. The resistor needs to be as close to the MIDDLE of the sender's range in order to behave correctly.
The Arduino natively understands 0-5v signals, so doing this turns them into a 0-1023 memory value that you can program the Arduino to do something with, such as moving a stepper motor, turn on a light, sweep over a LED bar graph, etc.
Here's an over-simplified example of what your desired code will basically do, using 10 LEDs for your intended display:
Read Pin 13 "Oil Pressure"
If Value =0~100, Write Pin 14 High (0-10 psi, Pin 14 has 5v)
If Value=101~200, Write Pin 15 High (10-20psi, Pin 15 has 5v)
If Value=201~300, Write Pin 16 High (20-30psi, Pin 16 has 5v)
and so on until you get to Value 1023 which is the LOWEST resistance the sender normally outputs (arduino sees 5v for this). Usually represents maximum oil pressure, max fuel, crazy stupid overheated engine, you get the idea.
You can see an example of the concept in action here, using a potentiometer to simulate the sender's signal:
https://create.arduino.cc/projecthub...r-graph-7e6212
Values may need to be tweaked to suit your senders' individual ranges, the real magic is all in the code. The above link includes an example of the code they used for it. Adjust the values to suit your needs and you'll be halfway there. Aaron Cake goes much further into Arduinos and cluster mods on his 1976 Cosmo here:
02-15-22, 12:35 AM
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You're in for an uphill battle. You might be worlds ahead going to an aftermarket ECU that supports a plug-in digital dash like Haltech.
Speedometers read in pulses. RPM is voltage I think. Oil pressure, fuel level, coolant temp is resistance. Idiot lights are circuits either going to ground or 12v.
To pull this off you'd need a deep knowledge of automotive 12v electronics, digital to analog conversion, microcontroller design and programming.....it's a big ask. Or just plug stuff in with a Haltech and make it work.
Or, just use the stock cluster that works just fine.
Dale
Speedometers read in pulses. RPM is voltage I think. Oil pressure, fuel level, coolant temp is resistance. Idiot lights are circuits either going to ground or 12v.
To pull this off you'd need a deep knowledge of automotive 12v electronics, digital to analog conversion, microcontroller design and programming.....it's a big ask. Or just plug stuff in with a Haltech and make it work.
Or, just use the stock cluster that works just fine.
Dale
I'm running my FD with a Link G4+ ECU with CANBUS capabilities, and I already thought on using that. The problem is that only he basic wiring to this Link is done, so everything related to indicators, or additional information not strictly necessary to make the ECU work, is not there and it would be even more work to get it.
Actually, what I have in mind is to create something simple that at some point, can replace OEM gauge cluster in case it gets broken (mine has odometer failing randomly) since they are quite rare and prices are going higher and higher.
Best regards.
02-15-22, 12:36 AM
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You should hook up with the guy that started this post - https://www.rx7club.com/3rd-gen-gene...-dash-1152372/
Looks like he's pretty far along at doing exactly what you're looking at doing, big exception being he appears to be designing his display to work with CAN bus, so it's better suited to aftermarket ECU's. Once you deep dive into the FD's FSM/wiring diagrams you'll soon see that the stock dash inputs consist of a gaggle of discrete analog & digital/switch inputs feeding instruments.
Looks like he's pretty far along at doing exactly what you're looking at doing, big exception being he appears to be designing his display to work with CAN bus, so it's better suited to aftermarket ECU's. Once you deep dive into the FD's FSM/wiring diagrams you'll soon see that the stock dash inputs consist of a gaggle of discrete analog & digital/switch inputs feeding instruments.
I'll contact him to check if he can help me somehow on my "project" (right now is just an idea).
Best regards.
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02-15-22, 02:20 AM
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In 2012, I built a simulator box that generated every signal a RX-7 cluster would receive. Fuel, Temperature, Oil Pressure are all Resistance meters, referenced to ground, while the Boost gauge is a 5v Voltage Divider (0-5v range). Speedo and Tach are 12v pulses, so I used an Arduino and suitable code with a keypad. Just input the frequency desired, press a button and see the gauge go to the corresponding reading. Per Granny's Speed Shop, 120hz signal on the Tach signal pin makes it read 3600rpm.
https://grannys.tripod.com/rx7tachrecal.html
As for the FC and earlier speedometers, I just used an extra speedometer cable with a household drill, using a Dimmer Switch to control the speed. The drill I used had a maximum speed of 3000rpm, so I calibrated the Dimmer switch by going up from 0 until the Speedometer hit 60mph (1024 rpm, close enough to 1000) and marked the Dimmer Switch's cover plate with "33%" to match.
If you REALLY want to build a digital cluster, similar to what was optional in a Z31 300zx, C4 Corvette, etc, I'd suggest starting with an Arduino. The Oil Pressure, Fuel Level and Temperature senders can be biased with resistors and then given 5v so they behave as a Voltage Divider, like the Map and TPS sensors do. The resistor needs to be as close to the MIDDLE of the sender's range in order to behave correctly.
The Arduino natively understands 0-5v signals, so doing this turns them into a 0-1023 memory value that you can program the Arduino to do something with, such as moving a stepper motor, turn on a light, sweep over a LED bar graph, etc.
Here's an over-simplified example of what your desired code will basically do, using 10 LEDs for your intended display:
Read Pin 13 "Oil Pressure"
If Value =0~100, Write Pin 14 High (0-10 psi, Pin 14 has 5v)
If Value=101~200, Write Pin 15 High (10-20psi, Pin 15 has 5v)
If Value=201~300, Write Pin 16 High (20-30psi, Pin 16 has 5v)
and so on until you get to Value 1023 which is the LOWEST resistance the sender normally outputs (arduino sees 5v for this). Usually represents maximum oil pressure, max fuel, crazy stupid overheated engine, you get the idea.
You can see an example of the concept in action here, using a potentiometer to simulate the sender's signal:
https://create.arduino.cc/projecthub...r-graph-7e6212
Values may need to be tweaked to suit your senders' individual ranges, the real magic is all in the code. The above link includes an example of the code they used for it. Adjust the values to suit your needs and you'll be halfway there. Aaron Cake goes much further into Arduinos and cluster mods on his 1976 Cosmo here: https://www.youtube.com/watch?v=HLoYRv2thwc
https://grannys.tripod.com/rx7tachrecal.html
As for the FC and earlier speedometers, I just used an extra speedometer cable with a household drill, using a Dimmer Switch to control the speed. The drill I used had a maximum speed of 3000rpm, so I calibrated the Dimmer switch by going up from 0 until the Speedometer hit 60mph (1024 rpm, close enough to 1000) and marked the Dimmer Switch's cover plate with "33%" to match.
If you REALLY want to build a digital cluster, similar to what was optional in a Z31 300zx, C4 Corvette, etc, I'd suggest starting with an Arduino. The Oil Pressure, Fuel Level and Temperature senders can be biased with resistors and then given 5v so they behave as a Voltage Divider, like the Map and TPS sensors do. The resistor needs to be as close to the MIDDLE of the sender's range in order to behave correctly.
The Arduino natively understands 0-5v signals, so doing this turns them into a 0-1023 memory value that you can program the Arduino to do something with, such as moving a stepper motor, turn on a light, sweep over a LED bar graph, etc.
Here's an over-simplified example of what your desired code will basically do, using 10 LEDs for your intended display:
Read Pin 13 "Oil Pressure"
If Value =0~100, Write Pin 14 High (0-10 psi, Pin 14 has 5v)
If Value=101~200, Write Pin 15 High (10-20psi, Pin 15 has 5v)
If Value=201~300, Write Pin 16 High (20-30psi, Pin 16 has 5v)
and so on until you get to Value 1023 which is the LOWEST resistance the sender normally outputs (arduino sees 5v for this). Usually represents maximum oil pressure, max fuel, crazy stupid overheated engine, you get the idea.
You can see an example of the concept in action here, using a potentiometer to simulate the sender's signal:
https://create.arduino.cc/projecthub...r-graph-7e6212
Values may need to be tweaked to suit your senders' individual ranges, the real magic is all in the code. The above link includes an example of the code they used for it. Adjust the values to suit your needs and you'll be halfway there. Aaron Cake goes much further into Arduinos and cluster mods on his 1976 Cosmo here: https://www.youtube.com/watch?v=HLoYRv2thwc
Correct, I'm starting this with Arduino and in case everything works, I will think moving it to a different platform.
Thank you very much for all this information, it is very usefull.
Best regards.
03-12-22, 12:34 AM
#10
You should hook up with the guy that started this post - https://www.rx7club.com/3rd-gen-gene...-dash-1152372/
Looks like he's pretty far along at doing exactly what you're looking at doing, big exception being he appears to be designing his display to work with CAN bus, so it's better suited to aftermarket ECU's. Once you deep dive into the FD's FSM/wiring diagrams you'll soon see that the stock dash inputs consist of a gaggle of discrete analog & digital/switch inputs feeding instruments.
Looks like he's pretty far along at doing exactly what you're looking at doing, big exception being he appears to be designing his display to work with CAN bus, so it's better suited to aftermarket ECU's. Once you deep dive into the FD's FSM/wiring diagrams you'll soon see that the stock dash inputs consist of a gaggle of discrete analog & digital/switch inputs feeding instruments.
I've looked into making my digital cluster a plug and play unit that would accept the factory connectors and act as an OEM replace unit. It could easily be done as long as you find/make your own female connectors but after thinking about it, I've decided to keep my gauge cluster bespoke as it makes my FD a little more "special". I'm honestly a beginner at programming and the work required to make this a commercially viable product is beyond what I want to put into it.
I love this kind of innovation with our cars though and I hope the FD chassis keeps evolving and keeping with the times. I'm definitely down to help whenever I can with anyone's project, just shoot me a PM with any questions.