Author Topic: Transistor overheating...  (Read 2513 times)

0 Members and 1 Guest are viewing this topic.

Offline MasterRykoTopic starter

  • Jr. Member
  • **
  • Posts: 9
  • Helpful? 0
Transistor overheating...
« on: July 11, 2007, 09:25:10 AM »
We are getting way too much heat from our transistor in our motor driver circuit.    We can't use a lower resistor because of current restrictions.  Are there any alternatives?  We need 1 amp to run our motor and we're using a TIP31 NPN transistor with a 340 ohm resistor and a 5 volt source.

Offline Tsukubadaisei

  • Robot Overlord
  • ****
  • Posts: 293
  • Helpful? 0
Re: Transistor overheating...
« Reply #1 on: July 11, 2007, 09:56:43 AM »
The heating is normal and inevitable. You must attach some metal(aluminium) plate to the back of your transistors(use those holes that big transistors usually have, they are supposed to be holes for screws) and/or install a mini brushless fan. I like fans, personally.
A.I.(yes those are my initials)

Offline KambeiX

  • Full Member
  • ***
  • Posts: 79
  • Helpful? 0
Re: Transistor overheating...
« Reply #2 on: July 11, 2007, 10:08:16 AM »
how much is the base current? it should be in the mA range but you could check anyways.

Also as Tsukubadaisei said, attach a heatsink and if heat is still too high (getting too close to 150°C for TIP31) then you must use a fan.


Offline Admin

  • Administrator
  • Supreme Robot
  • *****
  • Posts: 11,657
  • Helpful? 169
    • Society of Robots
Re: Transistor overheating...
« Reply #3 on: July 11, 2007, 05:46:28 PM »
For motor control you should use a MOSFET with a big 'ol heatsink on it, not a transistor.

Offline Brandon121233

  • Contest Winner
  • Supreme Robot
  • ****
  • Posts: 320
  • Helpful? 0
  • "Genius is %1 inspiration and %99 perspiration"
Re: Transistor overheating...
« Reply #4 on: July 11, 2007, 09:12:10 PM »
Well I would go with a H-Bridge, if its for motors, lots more features and simpler to work with than building your own H circuit out of MOSFETS
Hell, there are no rules here—we're
   trying to accomplish something.

                                                                              —Thomas Edison

Offline Tsukubadaisei

  • Robot Overlord
  • ****
  • Posts: 293
  • Helpful? 0
Re: Transistor overheating...
« Reply #5 on: July 11, 2007, 09:39:16 PM »
For motor control you should use a MOSFET with a big 'ol heatsink on it, not a transistor.


I agree that MOS-FET are easier to control than PN-junction transistor but there are printers that use PN transistors in their motor drivers. I dont know why but I think it depends on the case.
A.I.(yes those are my initials)

Offline KambeiX

  • Full Member
  • ***
  • Posts: 79
  • Helpful? 0
Re: Transistor overheating...
« Reply #6 on: July 11, 2007, 11:19:36 PM »
a mosfet is still a transistor.

For digital circuits it has many advantages, but if you compare:

a bjt transistor can achieve saturation with less voltage (though 5v is enough for many mosfets and even 3.3, 2v or less might be a problem)

If space is a concern, a bjt transistor can drive more current in less space.

But of course, they can handle higher temperatures, have less current consumption and are easier to implement as on-off switches.


Offline Tsukubadaisei

  • Robot Overlord
  • ****
  • Posts: 293
  • Helpful? 0
Re: Transistor overheating...
« Reply #7 on: July 12, 2007, 04:21:46 AM »
a mosfet is still a transistor.

exactly. just to make things clear:
Metal Oxide Semiconductor (electrical)Field Effect TRANSISTOR
A.I.(yes those are my initials)

 


Get Your Ad Here