On 2017-02-10 04:42 AM, alan.b.pearce@stfc.ac.uk wrote:
>>> This is why I suggested using a high side current sense chip like the L=
inear
>>> Technology LTC6101, LTC6102, LT6106 or Microchip PAC1921.
>>> These would work with a PCB trace at about that resistance and feeding
>>> that into an ADC would allow configurable current monitoring.
>> This sounds like a good idea.  Some nice chips here.. Just wondering if =
I put
>> the voltage out of these chips  into an ADC on my PIC if that would be f=
ast
>> enough to catch a short before my FET fries. I'll have to take a closer =
look at
>> the time it would take to read the ADC and take action. Because I am usi=
ng
>> PWM ( around 15 KHz ) I guess I would need to
>> synchronize my ADC reading with the on state.   I have read that FETs
>> can burn out fairly quickly ie. 10 uSec so the conversion and taking act=
ion to
>> turn off the FET would have to occur fast.
>> Jim
> I assumed that as you mentioned PWM control of the FETs that there would =
be a micro involved to drive the PWM, and that the current sense chip would=
 feed the micro. The micro would then handle a serial comms link to a PC fo=
r a source of commands re LED brightness etc., and to supply the PC with er=
ror/diagnostic information.
>
> There are PIC chips designed for motor control that have a current sense =
feedback input to allow the drive to the motor to be turned off but I don't=
 think these would act correctly for driving LEDs.
In this case there are no computers involved. The board will have an LCD=20
display for feedback. And yes there is a PIC controlling the PWM, LCD=20
display etc. I didn't realize there were PICs with current sense. I will=20
look in those.
Thanks for the help.
Jim
--=20
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