Author Topic: 3V3 device control 5V ESC?  (Read 1719 times)

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Offline mrburnzieTopic starter

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3V3 device control 5V ESC?
« on: January 17, 2020, 10:39:47 pm »
I have a dsPIC33 which produces a 3V3 PWM signal (50hz). It is ment for an ESC (cheap chinease one) 30A, but it doesn't react on 3.3V signal.

I have tried with an arduino mega (5V I/O) and everything works perfectly. I have compared the signal between the arduino and the dsPIC, the only difference is the voltage. On arduino works, dsPIC doesn't.

I got a level shifter (https://i.ebayimg.com/images/g/HtIAAOSwilVbpMWY/s-l640.jpg).

The problem is when I don't have the ESC powered, I get a 5V pwm output, but when I power the esc (as I must because they have to boot up on the max pwm duty cycle), the voltage drops back to 3.3V.

I have everything wired correctly, GND is all connected. Is this some impedance problem?  :-BROKE
"Talk is cheap, show me the code"

Anyone need of freelance software/hardware developer, hit me up!
 

Offline mrburnzieTopic starter

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Re: 3V3 device control 5V ESC?
« Reply #1 on: January 17, 2020, 10:46:10 pm »
"Talk is cheap, show me the code"

Anyone need of freelance software/hardware developer, hit me up!
 

Online ebastler

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Re: 3V3 device control 5V ESC?
« Reply #2 on: January 18, 2020, 01:04:51 pm »
I got a level shifter (https://i.ebayimg.com/images/g/HtIAAOSwilVbpMWY/s-l640.jpg).

The problem is when I don't have the ESC powered, I get a 5V pwm output, but when I power the esc (as I must because they have to boot up on the max pwm duty cycle), the voltage drops back to 3.3V.

I have everything wired correctly, GND is all connected. Is this some impedance problem?  :-BROKE

I can clearly see from the link you provided that your level shifter PCB is red. That obviously can't work.  ::)




Seriously though, a link to a technical description of the level shifter, and information on the chip it uses, would be much more useful than a small photo of several boards. Also, pardon my ignorance, what is an "ESC" to you? It's one of the more popular acronyms...
 

Online Zero999

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Re: 3V3 device control 5V ESC?
« Reply #3 on: January 18, 2020, 11:21:47 pm »
I Googled for HtIAAOSwilVbpMWY and got this ebay hit.
https://www.ebay.ie/itm/5Sets-4-Channel-Bi-Directional-Logic-Level-Shifter-Converter3-3V-5V-ForArduMA-PN/133166967704?hash=item1f015eab98:g:HtIAAOSwilVbpMWY

It appears to be a simple MOSFET level shifter, like the one Sparkfun sell.
https://learn.sparkfun.com/tutorials/bi-directional-logic-level-converter-hookup-guide/all


The only thing I can think of is the output impedance of the shifter is 10k, when the output is high and it's being loaded, pulling the voltage down.
 
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