GideonTech.com Forums

  • July 23, 2019, 11:06:50 AM
  • Welcome, Guest
Please login or register.

Login with username, password and session length
Pages: [1]   Go Down

Author Topic: transistor circuit design  (Read 2124 times)

trials_modder

  • Senior Modder
  • ***
  • Karma: +0/-1
  • Offline Offline
  • Posts: 174
transistor circuit design
« on: February 19, 2006, 04:34:36 PM »

i need help designing a circuit. There will be a motor that recieves constant power. If a switch is connected, I want the motor to run in the opposite direction, and when the switch is disconnected it runs in the original direction. I think it can be done using some NPN transistors, but I'm not sure.
Logged
LOUD ANGRY NOISES

viridius

  • Moderator
  • Elite Modder
  • *****
  • Karma: +15/-0
  • Offline Offline
  • Posts: 4,258
  • You know what I mean.
    • http://www.getyourlanon.com
Re: transistor circuit design
« Reply #1 on: February 19, 2006, 05:16:35 PM »

If you're using a physical device (as in a toggle switch), you can use a DPDT switch to flip the contacts.  If you only have a high-low logic input, you need to use an H-bridge.  What are you trying to do with this circuit?
Logged
"I'm totally going to send ninjas after you." - BalefireX

trials_modder

  • Senior Modder
  • ***
  • Karma: +0/-1
  • Offline Offline
  • Posts: 174
Re: transistor circuit design
« Reply #2 on: February 19, 2006, 06:05:14 PM »

A robot. Thanks to your guys' help in all my threads I've begun construction. I'll post a project log soon with pictures as it develops.

p.s. I've found out a NOT logic gate might do the trick.
Logged
LOUD ANGRY NOISES

viridius

  • Moderator
  • Elite Modder
  • *****
  • Karma: +15/-0
  • Offline Offline
  • Posts: 4,258
  • You know what I mean.
    • http://www.getyourlanon.com
Re: transistor circuit design
« Reply #3 on: February 19, 2006, 06:12:49 PM »

Careful, logic gates can only source a few milliamps.
Logged
"I'm totally going to send ninjas after you." - BalefireX

trials_modder

  • Senior Modder
  • ***
  • Karma: +0/-1
  • Offline Offline
  • Posts: 174
Re: transistor circuit design
« Reply #4 on: February 19, 2006, 06:29:35 PM »

resistors?
Logged
LOUD ANGRY NOISES

viridius

  • Moderator
  • Elite Modder
  • *****
  • Karma: +15/-0
  • Offline Offline
  • Posts: 4,258
  • You know what I mean.
    • http://www.getyourlanon.com
Re: transistor circuit design
« Reply #5 on: February 19, 2006, 07:26:43 PM »

what
Logged
"I'm totally going to send ninjas after you." - BalefireX

trials_modder

  • Senior Modder
  • ***
  • Karma: +0/-1
  • Offline Offline
  • Posts: 174
Re: transistor circuit design
« Reply #6 on: February 19, 2006, 10:26:04 PM »

So here's my plan:
Transistor circuits listen to parallel port pin and act as switch. If a pin is on then an alternate 5V power source will be connected and go to a series of more switches/logic gates. When a certain combination of pins is on, it will connect a certain circuit. May sound confusing/complicated but it will all make sense soon enough. Right now I am planning a way to have a circuit reverse its polarity if a pin is on/off, for driving a motor in forward/backwards direction.
Logged
LOUD ANGRY NOISES

viridius

  • Moderator
  • Elite Modder
  • *****
  • Karma: +15/-0
  • Offline Offline
  • Posts: 4,258
  • You know what I mean.
    • http://www.getyourlanon.com
Re: transistor circuit design
« Reply #7 on: February 19, 2006, 10:58:24 PM »

Yeah, an H-bridge made with FETs is perfect for the job.
Logged
"I'm totally going to send ninjas after you." - BalefireX

trials_modder

  • Senior Modder
  • ***
  • Karma: +0/-1
  • Offline Offline
  • Posts: 174
Re: transistor circuit design
« Reply #8 on: February 20, 2006, 11:24:39 AM »

Sorry, I'm not that fluent in electronics jargon. What's an H-bridge and FET?
Logged
LOUD ANGRY NOISES

viridius

  • Moderator
  • Elite Modder
  • *****
  • Karma: +15/-0
  • Offline Offline
  • Posts: 4,258
  • You know what I mean.
    • http://www.getyourlanon.com
Re: transistor circuit design
« Reply #9 on: February 20, 2006, 07:15:17 PM »

An H-bridge is the circuit I linked in my first reply.  It runs a motor in one direction or the other depending on the high/low state of a logic input.  FETs are power transistors designed to control high current loads from low power signals.  The page I linked has a guide for buliding an H-bridge with BJTs, Bipolar Junction Transistors.  If you're not using a ridiculously high power motor, they should work fine, too.
Logged
"I'm totally going to send ninjas after you." - BalefireX
Pages: [1]   Go Up
 

Page created in 1.422 seconds with 19 queries.