Bus Voltage Sensing Formula

JackyCheung · ‎2014-09-28

Posted on September 28, 2014 at 16:21

Gigi:

I'm in the Bus Voltage Sensing parameter settings of Workbench when the input voltage is 24V, I am a divider resistor R1 = 51K R2=1K, how to calculate excuse me my Bus voltage sensing network partitioning factor?

ã€€Best Regards

ã€€Jacky

Gigi · ‎2014-09-29

Posted on September 29, 2014 at 09:20

Ciao Jacky

Usually the Bus Voltage Sensing is done with a simple voltage divider.

Considering the one explained

http://en.wikipedia.org/wiki/Voltage_divider

you have to compute the Vin/Vout ratio that depends only on the resistors network: Vin is the DC bus voltage and Vout is the input of the ADC of the micro.

In your case, I assume that the R2 is between Vout and ground.

Bus Voltage Sensing = (51K + 1K)/(1K) = 52

This mean that you are scaling 52 times the DC bus voltage -> 0.46V to ADC (exploiting small part of the range. Maybe the petitioning factor can be improved).

Ciao

Gigi

JackyCheung · ‎2014-09-29

Posted on September 29, 2014 at 18:29

Thank you, the problem is solved.

mikemike9141 · ‎2014-09-30

Posted on September 30, 2014 at 09:54

Hi Gigi,

I would like to comment on a possible improvement on that configuration item. I also stumbled on this for a moment because

- on other locations, the tool asks for a gain (for example, current sensing), which is more straight forward in my opinion.

- for the bus voltage, I can only enter an integer value. In my design, the attenuation factor isn't.

- in the resulting header file, this number is indeed converted into a (floating point) gain.

Regards

Frank