+3
Under review

Digital out channel (DOUT) high frequency buzzer noise?

J Kelly 1 year ago in Master modules / MD4 updated by Chris Litwin 5 months ago 7

I have connected a buzzer to my MD4-7 inch display using the DOUT channel. 

The signal receives high frequency noise when it is not triggered. Could this be related to the diagnostics tests for internal faults?  - If so how can it be switched off via IQAN design. 

Interesting. The MD4 low-side digital out is only checking for voltage to diagnose off state open load, I cannot see how this would cause the buzzer to give a noise. 

The leakage current is quite small, less than 200 uA, but I wonder if this could be enough make the buzzer give this sound. 

This is interesting, I've experienced similar issues with DOUTS on MC2's . I was using incandescent indication lights on DOUT channels. They would be ever so slightly illuminated when the DOUT was "OFF". My first workaround was adding a load resistor to across the Bulb, but eventually used a relay. 

+1

We have the same issue using an MD4 DOUT LS and an alarm buzzer. I have also tried it with an incandescent light with same result. An LED does not have the issue though. The alarm was ECCO # 201120. I just tried it out on an MC43 DOUT LS and the buzzing is a lot less audible. Next I tried disabling the open load detection on the DOUT and the buzzing went away. Is it possible to add the option to turn off the open load detection on the MD4? It would be nice to not need to add the additional resistor for load or use a relay.

Under review

Had to check this one with a colleague, I wasn't aware that the open load detection on the Digital out LS on the MC43 had an influence on the leakage current. 

With off-state open load detect enabled on the MC43 Digital out LS, leakage is up to 200 μA. 

With off-state open load detect disabled on the MC43 Digital out LS, leakage is < 5 μA.



Gustav,

Is there any possibility of having the option to lower the leakage on the MD4?

Thanks,

Chris

+1

I know the option to disable open load on MD4 DOUT has been requested in the past. I believe that if it is implemented in the same way as for the MC43, it would reduce leakage. 

I'll enter it as a feature request in our case tracker.