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USB drops out

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Member Admin

Resistorized plugs are almost mandatory :-). I would go for that in any case! Cables are good to check too.

Posted : 31/12/2020 3:49 pm

OK, tried to wrap aluminium folie around the sparkplugg wires....dont do that..sparks jumping between the wires and noise got worse ! After installing resistor plugs and isolate the wire from load cell about 3-400mm out from the cell the noise went down and the USB is more stable.

At max RPM USB signal on bluebox can flicker from green to yellow ...but not red the end of the run but still not goes down.

So Im almost OK for now and will see whats happens in future.

This engine Im running now has distributor with mechanical points...mabe thats bad comp to eletronic pick up ?? What do you guys think??

Topic starter Posted : 05/01/2021 1:50 pm
Member Customer


Today I spent some hours troubleshooting and re-wiring. With some of my motors, the comm drops as soon the motor is started. with other the dyno works ok.

I noticed that 3 of 5 load cells has the cable shield connected to the cell body - bad
The one I have on the dyno as well. After cutting the shield, the comm get better.

Connecting the chasys to the water pipe helps as well.
It works in manual brake mode, but as soon I make a sweep, comm is lost.

Tried with New PVL coil and Denso IK31 6k ohm plug - the same - comm drops.

The most problematic is the EGT, standard sensor from BMW / Denso. It gas 300mm original sensr not shielded wire and then 1500mm shielded cable. no idea what to do here.

@Jostein. Do you have any noice suppressing components on the inputs, like aux, Lcell and K ???
Something need to be done here.
@Jostein - If you have some spare I / O on the MCU, can you try WiFi or BT conn to PC? This may solve the problems at once.
I volunteer for the tests.




This post was modified 11 months ago by Pavlik Marinov
Posted : 16/01/2021 8:00 pm
Member Admin


Yes, shield must only be connected in one end, that is very important, otherwise you can get electromagnetic induced current in the shield, which will cause problems. 

On all inputs and outputs there are components to protect the board. Inputs and outputs are not isolated. 

One thing that can be used is a USB isolator with separate power supply. This one for example: USB Isolator for Protection of all types of USB devices (


Posted : 16/01/2021 8:19 pm
Member Customer

USB isolator is very good idea, I ordered from my source and will report when it arrive.

having the source of the disturbances identified as the ignition components, I have the doubts at which end of the USB the comm fails, blue box or PC.

If the disturbances are induced to the sensor cables (load cell, EGT and others) they may affect the comm between blue box and USB isolator as well...

Meantime I may apply some shielding Technics used in aircraft piston engines.....



Posted : 17/01/2021 11:24 am
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