SimHub Tach Dash Gauge

A lot of people (including me) have issues making these nice Auto Tachometer Gauges to works in SimHub:



The DynoRacing Tach Gauge one is common choice, it is supposed to be pretty straightforward project, but like most of you mine did not work out of the box. It is nice as is large enough, have multiple color backlight and also built in Shift Light. The Shift Light is very easy to be set up to be controlled by Tach itself or in SimHub. In my setup i managed to configured it through Tach to light up at the same time as my SimHub Gear indicator.

As configuration for me was hit and miss and still does not properly I will be recording in this topic all my findings and try to get to the bottom of it.

Main Considerations:
1. SimHub Documentation states you should configure Arduino pin 9 signal to be between 2.5-3V - I did not find any means to do so
2. Based on above I measured signal for several Arduinos I had at hand as follows:​​​​​
- Arduino Pro Micro Signal Pin provides between 2.37V to 2.42V signal
- Arduino Uno R3 gives 2.40-2.45V, a little more stable out of the box
- Arduino Nano (Mini USB connector, old bootloader) was giving below 2.35V - was totally unusable
N.B.! - all these Arduinos are clones and presumably will give different results
3. The modern Tachs these days are PWM controlled (including the DynoRacing one) and it is possible to control them directly from signal pin
4. Tach itself is powered from 12V external PSU
5. Tach GND is connected to Arduino GND
6. I measured signal both with Transistor amplifier Circuit and without - signal was same voltage

I tested the project both with and without the transistor circuit. Personally could not make it run with the circuit, removed it and started paying around with direct pin9 connection. Again hit and miss, here is what I figured in the process:

Arduino Pro Micro:
Setup - Got it running through powered USB hub. Without the external power the arrow did not work at all.
Performance - Poor. Would work from time to time properly, most of the times arrow would just jump around. In 30% of the occasions the Tach would not move at all. Quite unstable, not really applicable.

Arduino Uno R3 - no external power:
Setup - Tested connected both to Motherboard and PCI-E riser USB powered card. Behaves the same. Tested in powered USB hub - was worse (presume the Pro Micro could be better directly connected to MB USB)
Performance - Most of the times it works well. Has occasional jitter but much better. With slow/not so powerful cars is quite OK. With powerful cars which can change Revs quickly Tach Arrows jitters in these changes.

Arduino Uno R3 - 5V external power:
Setup - Same as above but Arduino is powered through barrel connector with 5V from Computer PSU (trying to avoid any additional EMI)
Performance - No visible difference from above

Conclusions:
1. The Tach jitter is mainly based on the low PWM signal
2. Switching to Arduino with higher voltage signal improves it a little
3. Transistor circuit is not needed but presumably will fix the sudden changes jitter

Things that can be improved and will test:
1. Powering the Uno with higher voltage - intend to use 12V from the Tach PSU (Uno is supposed to handle 5-12V input)
2. Rebuild the Transistor circuit - never tested it with UNO, have to verify how it works with it
3. My Arduino Uno looses constant connection - this happens a lot with cheap Arduinos - after some time they just do not work properly. Waiting new one to arrive to test with it.
4. Will test with separate Arduino (mine has aRGB LED lights + Rumble Motors + Tach + Time display on it - pretty heavy configuration)

Will keep updated the topic here, hope finally it starts working properly.

I completed testing and it works very well now.

Removed the aRGB lights from the sketch - they were overloading the Arduino when using complex animations.
Powered the Arduino Uno with 12V externally - this solved my issues.
Rebuild the Transistor circuit - as expected the Tach stopped working with it. The new PWM Tachs apparently need to be directly controlled from the Data Pin.