2N2222 transistor to drive a motor ????

A

Ankur

Guest
How much current can the 2N2222 transistor bear? Can it drive a motor
? I tried doing tht but it got heated up and hFE started changing
thereby causing the current to increase gradually . The config. i used
was as follows :-



^ ^ Vcc =25V
! !
100k 220ohm
! !
MotoR !
! /
--------B---
\
!
GND

collector current flowing was of the order 100mA ( which increased
with time due to heating up of transistor )
Vcc might seem a lil high but below tht , the motor cudn't drive .

Basically , i need to drive a motor from a digital +5V ... the above
circuit was just 2 test the current capacity .
I also wanna know whether an AND gate output can drive this ? It was
switching the transistor perfect but collector current was too small .
*******************************************************************************
 
"Ankur" <ankur127@yahoo.com> wrote in message news:fb5b742e.0402240241.4c045700@posting.google.com...
How much current can the 2N2222 transistor bear? Can it drive a motor
? I tried doing tht but it got heated up and hFE started changing
thereby causing the current to increase gradually . The config. i used
was as follows :-



^ ^ Vcc =25V
! !
100k 220ohm
! !
MotoR !
! /
--------B---
\
!
GND

collector current flowing was of the order 100mA ( which increased
with time due to heating up of transistor )
Vcc might seem a lil high but below tht , the motor cudn't drive .

Basically , i need to drive a motor from a digital +5V ... the above
circuit was just 2 test the current capacity .
I also wanna know whether an AND gate output can drive this ? It was
switching the transistor perfect but collector current was too small .
Click to expand...

The current capacity should be ok if you connect the motor correctly. Replace the 220 ohm resistor with the motor and the 100K
resistor with a 4.7K.

Hope that helps.

Tim
 
You also might want to put a diode (like 1N4001) in parallel with the transistor, anode to the emitter and cathode to collector.
That will prevent flyback voltage from damaging the transistor when the current flow is cut off by the transistor. This applies also
to relays or any inductive device.

Tim

"Ankur" <ankur127@yahoo.com> wrote in message news:fb5b742e.0402240241.4c045700@posting.google.com...
How much current can the 2N2222 transistor bear? Can it drive a motor
? I tried doing tht but it got heated up and hFE started changing
thereby causing the current to increase gradually . The config. i used
was as follows :-



^ ^ Vcc =25V
! !
100k 220ohm
! !
MotoR !
! /
--------B---
\
!
GND

collector current flowing was of the order 100mA ( which increased
with time due to heating up of transistor )
Vcc might seem a lil high but below tht , the motor cudn't drive .

Basically , i need to drive a motor from a digital +5V ... the above
circuit was just 2 test the current capacity .
I also wanna know whether an AND gate output can drive this ? It was
switching the transistor perfect but collector current was too small .
*******************************************************************************
Click to expand...
 
"Ankur" <ankur127@yahoo.com> wrote in message
news:fb5b742e.0402240241.4c045700@posting.google.com...
How much current can the 2N2222 transistor bear? Can it drive a motor
? I tried doing tht but it got heated up and hFE started changing
thereby causing the current to increase gradually . The config. i used
was as follows :-



^ ^ Vcc =25V
! !
100k 220ohm
! !
MotoR !
! /
--------B---
\
!
GND

collector current flowing was of the order 100mA ( which increased
with time due to heating up of transistor )
Vcc might seem a lil high but below tht , the motor cudn't drive .

Basically , i need to drive a motor from a digital +5V ... the above
circuit was just 2 test the current capacity .
I also wanna know whether an AND gate output can drive this ? It was
switching the transistor perfect but collector current was too small .

****************************************************************************
Click to expand...
***

All Bipolar transistors change gain with heat!

There are sacrificial methods of stabilizing the transistors gain.

BUT! You are misssing the point!

Your circuit only wants to be a SATURATED driver. (On-Off Switch)
So drive the base with the MOST current necessary to maintain saturation in
the worst case.
You have not said what generation your AND gate is, so I have no idea if it
can drive the base
correctly in current.


--
*
| __O Thomas C. Sefranek WA1RHP@ARRL.net
|_-\<,_ Amateur Radio Operator: WA1RHP
(*)/ (*) Bicycle mobile on 145.41, 448.625 MHz

http://hamradio.cmcorp.com/inventory/Inventory.html
http://www.harvardrepeater.org
 
Change that to read...

Put the diode in reverse polarity across the motor.

My bad. I violated my own prime directive. "Start brain before engaging mouth..."

Tim

"Tim Dicus" <tim@prolectron.com> wrote in message news:yAG_b.1649$UU.1501@lakeread01...
You also might want to put a diode (like 1N4001) in parallel with the transistor, anode to the emitter and cathode to collector.
That will prevent flyback voltage from damaging the transistor when the current flow is cut off by the transistor. This applies
also
to relays or any inductive device.

Tim

"Ankur" <ankur127@yahoo.com> wrote in message news:fb5b742e.0402240241.4c045700@posting.google.com...
How much current can the 2N2222 transistor bear? Can it drive a motor
? I tried doing tht but it got heated up and hFE started changing
thereby causing the current to increase gradually . The config. i used
was as follows :-



^ ^ Vcc =25V
! !
100k 220ohm
! !
MotoR !
! /
--------B---
\
!
GND

collector current flowing was of the order 100mA ( which increased
with time due to heating up of transistor )
Vcc might seem a lil high but below tht , the motor cudn't drive .

Basically , i need to drive a motor from a digital +5V ... the above
circuit was just 2 test the current capacity .
I also wanna know whether an AND gate output can drive this ? It was
switching the transistor perfect but collector current was too small .
*******************************************************************************
Click to expand...
 
Subject: Re: 2N2222 transistor to drive a motor ????
From: "Thomas C. Sefranek" WA1RHP@ARRL.NET
Date: 2/24/2004 5:49 AM Central Standard Time
Message-id: <P42dnRnbXcQXp6bdRVn-hA@comcast.com

All Bipolar transistors change gain with heat!

There are sacrificial methods of stabilizing the transistors gain.

BUT! You are misssing the point!

Your circuit only wants to be a SATURATED driver. (On-Off Switch)
So drive the base with the MOST current necessary to maintain saturation in
the worst case.
You have not said what generation your AND gate is, so I have no idea if it
can drive the base
correctly in current.


--
*
| __O Thomas C. Sefranek WA1RHP@ARRL.net
Click to expand...
Tom is right -- you're getting heating on your 2N2222 because it's not
saturating. A saturated NPN transistor will have a Vce (voltage between
collector and emitter) of around 0.3V or less. Power across the transistor is
calculated as Vce * I. If you've got 2 or 3V across your transistor, and
you're driving a 100 mA load, your power dissipation will be high (200 to 300
mW).

Digital logic gates have specified maximums as far as how much current they can
drive, and you didn't specify which logic gate you're using to drive the
transistor. As a result, can't give you more than general advice about how to
do this.

If you've got a TIP120 (available at Radio Shack), you might want to try this
circuit -- it will work for any logic gate operating at 5VDC (view in fixed
font or M$ Notepad):

Logic Motor Driver
VCC
|
o---------.
| |
.---o----. |
| + | |
| | |
| | |
Motor (100 mA)| - 1N4002
| | ^
| | |
| - | |
'---o----' |
| |
o---------'
10K |
___ |/ TIP120
o----|___|-o-----| NPN DARLINGTON
Logic Input | |>
.-. |
10K | | |
| | |
'-' |
| |
=== ===
GND GND


A saturated darlington will have a little more than 1V from collector to
emitter. You'll then have 1V * .1A = .1W across the darlington, so you won't
need a heat sink.

Good luck
Chris
 
By the way, you might want to try downloading a freeware copy of

Andy´s ASCII-Circuit v1.24.140803 Beta

available at

http://www.tech-chat.de/

It's very helpful for batting out snippets of circuits for text only
newsgroups.

Good luck
Chris
 
it looks like your not saturading the transistor enough.
this can lead to heating because the junctions are not at
their lowest resistance point.
if over speed is an issue then place a dropping resistor at the
emitter to componsate for the over speed. this way you can keep the
transistor at saturation but it may cause poor regulation if load
varies on the motor.

if you don't need variable speed then use a HexFet transistor they
can switch on at very low resistance thus causing far less heating.



Ankur wrote:

How much current can the 2N2222 transistor bear? Can it drive a motor
? I tried doing tht but it got heated up and hFE started changing
thereby causing the current to increase gradually . The config. i used
was as follows :-



^ ^ Vcc =25V
! !
100k 220ohm
! !
MotoR !
! /
--------B---
\
!
GND

collector current flowing was of the order 100mA ( which increased
with time due to heating up of transistor )
Vcc might seem a lil high but below tht , the motor cudn't drive .

Basically , i need to drive a motor from a digital +5V ... the above
circuit was just 2 test the current capacity .
I also wanna know whether an AND gate output can drive this ? It was
switching the transistor perfect but collector current was too small .
*******************************************************************************
Click to expand...
 
"2N2222 datasheet" in google nets multiple links to sources for the data.
 
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