Noisy TPS if bluetooth is not supplied from the recommended "wired-in" dedicated 5V supply and no additional regulator (or added cap is used).
If really using EC36/28 as a source of +5V supply for BT module, a 68uF (or greater, eg. 100uF 10V,16V or even 25V is not too big mechanically) on the 5V inside the DSUB9 housing (C- on DSUB9/pin5=GND C+ on DSUB9/pin9=+5V obviously).
- Most effective NEAR the BT, (not near v3 or inside v3), successfully pushed down noise to below reasonable "TPSdot" level
- EC36/28 was designed for MAP and HALL sensors, and not for spiky loads. It has been improved (better specs regulator used), and considering adding even more caps inside but cannot fully substitute the cap NEAR BT module
Topic for discussion.
In 2016 I experienced noisy 5V supply on Genboard V3.8 , usually when Vems bluetooth adapter is powered from EC36/28. I have not been alone.
So one more confirmation that powering BT from EC36/28 (which is primarily for HALL and MAP sensors) is not a good idea, and there is a good reason for the "wired in" option (which is a dedicated powerful supply) for the bluetooth module.
- Doctor, it hurts if I do this...
- don't do that than :-)
The bluetooth adapter generate noise on +5V supply (sudden high current when transmitting), effecting MAP and TPS if used from same supply (eg EC36/28). In our application TPS DOT rate settings caused acceleration enrichments to be active ALL the time, while little added, it held off EGO and VemsTune and VemsDisplay? gauges would flutter significantly.
- Adjusting TPS DOT rate settings can cure the symptom
- solution: External power supply of the Vems bluetooth adapter resolved the issue..
Today while looking at the schematics for another modification, I noticed that C69 (220n) capacitor on 5v feeding EC36/29 is not present on the board. Pin 29 is powered from Pin 28 via R142 and ground through C69.
Would installing a capacitor help reduce the noise generated by the Vems bluetooth adapter on EC36/28?
- inside v3: helps a little, not perfect
- A 68uF cap closer to the BT, inside the DSUB9 helps though.
- powering from separate [regulator] (this fits in a small heatshrink, if someone does not like the size of the big overmoulded 3A 5V supply)
- perhaps adding more cap, eg. 10uF (fast ceramic eg. 1206; or 1uF ceramic and 22..47uF electrolitic in parallel) on EC36/28 helps (because bluetooth supply current spikes are sharper than any HALL or MAP sensor supply current).
- tested: 68uF or greater works well if NEAR the BT eg. in the DSUB9, between DSUB9 pin5 and pin9 (either side of the DSUB9, easier and feels better inside the female)
- (or using +5V from LCD connector or header or PS2 so close to endplate that unclamping of ECU not needed to access it, no full disassembly=minimal time and risk).
- In any case, the proper way is to use a separate regulator independent of HALL, MAP, TPS (or other essential engine control)
- also possible: order comment when ordering VEMS ECU: "RS232 on DSUB9-female with +5V on pin9" (free of charge).
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