motor startup: how to automatize it and give it a low pulse?

[Beffo]

uc2625 application

I'm using UC2625 to drive a bldc motor. Works great with the typical application circuit in datasheet.

But you have to give it a nudge just to get it started... then it accellerate fast wich is great.

So how do I make it start automatic?

Added after 1 hours 24 minutes:

OK, What I should do to give the brake pin 21 a low pulse to start it up...

Well how do I make this pulse?

https://pdf1.alldatasheet.com/datasheet-pdf/view/29340/TI/UC2625.html

 

[IanP]

Re: About motor startup...

Take a look at this application note:
"UC2625/3625 Start-up Problem
Application Note
PCN# 20040521000A"
https://mist.ext.ti.com/pcn%5Ci_rep1.nsf/0/862569A90052406086256F2B0076E31B/$File/PCN20040521000A_Final.pdf?OpenElement

Regards,
IanP

 

[Beffo]

Re: About motor startup...

IanP:
I have already looked at that App. Note... It is written to avoid failure.

My motor diddn't even start up.

After trial and error I foud that the pin "brake" need a low pulse to get a flank that the "hall measure circuit" can react on.

The solution was a RC-circuit switching a npn-transistorn to open collector after a certain time.