Author Topic: having issues building a motor driver  (Read 724 times)

0 Members and 1 Guest are viewing this topic.

Offline cold-steelTopic starter

  • Newbie
  • Posts: 4
  • Country: gb
having issues building a motor driver
« on: June 24, 2019, 03:05:37 pm »
i am using a irf510 n channel mosfet and a 10k pull down resistor in order to control a motor that is connected to the wire in parallel with the diode. it only turn on when i touch the metal which gets it tot turn on and off, or if i connect the gate to the 12v power line.

connecting the resistor to the 12v line and plugging the wire on that line or taking it off has the desired effect but it doesn't work when i use the 555 timer output. I'm guessing that the problem might be with the power supplies. the pull down resistor only works on the 12v line.
 

Offline cur8xgo

  • Regular Contributor
  • *
  • Posts: 148
  • Country: us
Re: having issues building a motor driver
« Reply #1 on: June 24, 2019, 03:09:20 pm »
i am using a irf510 n channel mosfet and a 10k pull down resistor in order to control a motor that is connected to the wire in parallel with the diode. it only turn on when i touch the metal which gets it tot turn on and off, or if i connect the gate to the 12v power line.

connecting the resistor to the 12v line and plugging the wire on that line or taking it off has the desired effect but it doesn't work when i use the 555 timer output. I'm guessing that the problem might be with the power supplies. the pull down resistor only works on the 12v line.

Draw a schematic?

Is 555 output above the IRF510 gate threshold?

Do you have a way of confirming your 555 output is working at all?
 

Offline garethw

  • Regular Contributor
  • *
  • Posts: 88
  • Country: gb
Re: having issues building a motor driver
« Reply #2 on: June 24, 2019, 03:20:31 pm »
In addition to previous comment, make sure your mosfet is ‘below’ your motor I.e the motor is connected to power and is grounded through the mosfet. This is because you need you gate voltage to be, say, 10v higher than the source.  If you put the motor after the mosfet the source is only a few mV lower than the gate and the mosfet won’t turn on fully or at all.


Sent from my iPhone using Tapatalk
Father
Husband
MENG Electronic Engineering student
 

Offline ArthurWozniak

  • Newbie
  • Posts: 6
  • Country: br
Re: having issues building a motor driver
« Reply #3 on: June 29, 2019, 01:12:24 am »
Hey,

Did you connect GND from 7v and 12v together?
If you can, try to use push-pull circuit with complementary transistors to drive the MOSFET,

Best regards,
 

Offline ptricks

  • Frequent Contributor
  • **
  • Posts: 672
  • Country: us
Re: having issues building a motor driver
« Reply #4 on: June 29, 2019, 10:52:43 am »
I suspect what is happening is the 555 output isn't above the gate threshold for the mosfet long enough to complete the turn on before switching back off, the wave form is probably not a solid 10+ volts but rather a deformed one with just the peaks at close to voltage for the mosfet. Motors have a large in-rush current when they start and with the on/off input of the 555 the mosfet is experiencing a lot of surges + high resistance from not turning on fully which makes it run hot.

You can do as suggested and try to drive it with transistors or an easier route would be to use a logic level mosfet .



 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf