Hi,

I have a set of bluetooth (rally)buttons that use BT to control the (navigation) tablet on a motorcycle. Tablet is powered from its internal battery (not connected to motorcycle power).
The buttons/bluetooth dongle can be powered by 12V power source.
When I power the buttons from motorcycle power system then the buttons send occasional button presses to the tablet.
When I power the buttons from standalone battery, everything works, no random button presses.

So my uneducated guess is that power source quality somehow messes with the BT buttons.

These are URSAE buttons so I do not have access to the hardware nor software. I have tried contacting manufacturer, but no sensible feedback from there unfortunately.

Any advice on how to troubleshoot the problem and possibly fix? At the moment the fix is that I am using the battery to power the buttons. I have tried using dc-dc isolated 12v-12v power supply module to fix the issue, but the issue persists.

Thanks for any ideas!
Eric

 

OK, the button module can be powered by an external power source. What is required is both a voltage regulator and a noise filter. Have you measured the voltage that the motorcycle power source actually delivers??
Does the motorcycle have a battery??

 

Hi, thanks for the questions.
Motorcycle has a 12V battery. The charging current measured is 14,4V. I also tested the simple DC-to-DC step down converter to take the voltage to 12V. The behaviour continued the same with the converter.

The behaviour is that actually one button press is sent every 6-10 seconds. So it is not like constant random button presses, but rather intermittent.

Then bought the DC-DC isolated power supply module (https://www.aliexpress.com/item/1005004468412624.html), that outputs 12V exactly, but the issue remained the same.

I also tested taking power from motorcycle power harness (just in case there was an issue with power cutting out ) and alternatively also directly from motorcycle battery that is connected. When motorcycle does not run, the system works correctly, but when bike is running the button press is sent in random intervals for both cases.

What else could I try?

 

I suggest a series power filter for both the positive and negative feed from the battery. probably three stages, first a choke, next a capacitor another choke, and a second capacitor after that. And hopefully those buttons will function with only a ten volt supply.

Another option would be to power them from a separate battery, with the battery to buttons wires isolated from the bike power ground, and charging that small separate battery thru two high value resistors, one in each lead from the bike battery. Those resistors sized to provide a very minimum float charge current.

 

Thanks for the ideas.
I have been using the 9V 6LR61 battery to power the buttons without a problem. So I assume 10V is enough.
Will order parts and test it out, this will take some time.

 

OK, what is important will be to assure that the resistance is enough to limit the charge current to less than the allowed trickle charge current. That will not be very much, so the resistance will be quite a bit.

 

Thanks, I am investigating the first solution that MisterBill proposed.
If I take the power from motorcycle power harness and add the filter close to the load (BT buttons), then would this be correct schematics?

View attachment 352811

And is it ok to use following values?
L1 and L2 = UU9.8 20MH (they are double coils)
C1,C2,C3,C4 = for each C three different size capacitors in parallel 0.1µF | 1µF | 10µF ceramic 50V

 

On my end, clicking the attachment gave me an "error 403"

 

Hi, thanks for pointing out. Seems that just pasting in the image did not work. Here is the image inserted by attaching files.

 

That is the circuit that I was describing!!

 

Hi, I built the system as described above. Unfortunately it did not solve the issue. It did improve the situation a little, now the button press is less frequent, but still happens quite often when riding.

Not sure if I should try to shield the entire thing or use special shielded cables or add an element to the mix?

As said when the buttons are powered from separate battery (9V 6LR61) the problem does not occur.

 

One more question: Do the unintended "button presses" coincide with bumps or other vibrations??
Are you able to add one more capacitor across? Between the positive and the negative, at the last connection before the outgoing power cable?? The capacitor could be at least one MFD, or more.

 

Hi,

I am not sure about the bumps, but what I have noticied is that if the bike is stationary there are less button presses. I tested so that the motor was running, bike was not in gear and I just played with throttle. There are button presses once per 20 seconds or so. When riding a bike on tarmac, the button presses were maybe once per 5-10 seconds. So there might be something there.

I can fit in the additional capacitor will add that to the mix and test again. I presume it is at least on microfarad?

 

Both larger and lesser capacitors can be useful. The lower value capacitors also, usually, have less self inductance. So they bypass higher frequency signals. Certainly motor circuit noise is often a problem. You can also add capacitors directly between the + and- sides in the filter that you added.