Motor control via parallel port?

M

mike

Jan 1, 1970
0
Hi,

Trying to control a 12V 5A motor from the parallel port. I have to control
ten of them, so I'm trying to get away without using expensive relays or
optoisolators ($20-$30 each). I found a monolithic darlington transistor
rated at 10 amps, already including reverse-current diodes and appropriate
resistors, perfect for my application (so it seems).

I'm planning on hooking up a low current cheap optoisolator/interrupter to
drive this transistor from the parallel port (albeit high voltage isolation)
so I have a good chance of not frying the computer if one of the motors
overheat or blows. Would this work for my application?

Any help would be appreciated.

http://rocky.digikey.com/WebLib/Fairchild/Web Data/TIP140_141_142.pdf

Thanks!

J

John Popelish

Jan 1, 1970
0
mike said:
Hi,

Trying to control a 12V 5A motor from the parallel port. I have to control
ten of them, so I'm trying to get away without using expensive relays or
optoisolators ($20-$30 each). I found a monolithic darlington transistor
rated at 10 amps, already including reverse-current diodes and appropriate
resistors, perfect for my application (so it seems).

I'm planning on hooking up a low current cheap optoisolator/interrupter to
drive this transistor from the parallel port (albeit high voltage isolation)
so I have a good chance of not frying the computer if one of the motors
overheat or blows. Would this work for my application?

Any help would be appreciated.

http://rocky.digikey.com/WebLib/Fairchild/Web Data/TIP140_141_142.pdf

Thanks!

Those darlingtons are marginal on their current capability. It is
true that under some conditions, they can stand a 10 ampere current,
but the gain curve that just makes it to 10 amperes specifies that
there is 4 volts across the device. Are you willing to have your 12
volt motor supply waste 4 volts across the transistor when the motor
draws 10 amperes? A motor rated for 5 ampere drain will allow quite a
bit more than 5 amperes pass during start up or stall. I would look
into finding a big MOSFET to do the switching. One with an on
resistance of less than (4 volts / 10 amperes)= 0.4 ohms would beat
the darlington. For example, the NDP603AL has an on resistance of
..022 ohms which would waste only .022*10=.22 volts during a 10 amp
surge. It is rated for 25 amps continuous duty, 100 amperes peak. It
sells for $.087 each if you order 10 from Digikey. http://www.fairchildsemi.com/ds/ND/NDP603AL.pdf One other point... The diode that is internal to this device will not protect the device during turn off. This protects the device from applied reverse voltage. The motor produces a reverse voltage when it is switched off, but this reverse voltage effectively adds to the 12 volt supply so as to increase the total voltage applied to the switch, not reverse it. You will need additional diodes, one across each motor, to clamp the reverse voltage they create. But the total energy is pretty small (if the motor doesn't get forced to turn backwards) so a 1 amp diode (1N4000) is probably plenty big. S Si Ballenger Jan 1, 1970 0 Hi, Trying to control a 12V 5A motor from the parallel port. I have to control ten of them, so I'm trying to get away without using expensive relays or optoisolators ($20-$30 each). I found a monolithic darlington transistor rated at 10 amps, already including reverse-current diodes and appropriate resistors, perfect for my application (so it seems). I'm planning on hooking up a low current cheap optoisolator/interrupter to drive this transistor from the parallel port (albeit high voltage isolation) so I have a good chance of not frying the computer if one of the motors overheat or blows. Would this work for my application? Any help would be appreciated. You can get the transistor from radio shack and make a test rig using three 1.5v batteries in series (~4.5v) going through a 2.2k resistor (~2ma current) to simulate the parallel port control. If you need more current through the darlington base, you could use a common npn transistor controlled by the parallel port to put some higher current in fom the 12v supply instead of from the parallel port. I Ian Stirling Jan 1, 1970 0 Those darlingtons are marginal on their current capability. It is bit more than 5 amperes pass during start up or stall. I would look into finding a big MOSFET to do the switching. One with an on resistance of less than (4 volts / 10 amperes)= 0.4 ohms would beat the darlington. For example, the NDP603AL has an on resistance of .022 ohms which would waste only .022*10=.22 volts during a 10 amp surge. It is rated for 25 amps continuous duty, 100 amperes peak. It sells for$.087 each if you order 10 from Digikey.
http://www.fairchildsemi.com/ds/ND/NDP603AL.pdf

Another nice thing about MOSFETs is that if you don't care about speed
(and with motors, you don't much) you can reduce or eliminate the
need for a diode by picking the series resistor appropriately.
This also reduces the likelyhood of damage to the driving gate if things
go wrong.
100K or so might be the right ballpark.
(too slow, and the transistor spends too long in linear mode, and will
heat up much. If you want to do PWM, this is a bad idea)

T

the Wiz

Jan 1, 1970
0
mike said:
Hi,

Trying to control a 12V 5A motor from the parallel port. I have to control
ten of them, so I'm trying to get away without using expensive relays or
optoisolators ($20-$30 each). I found a monolithic darlington transistor
rated at 10 amps, already including reverse-current diodes and appropriate
resistors, perfect for my application (so it seems).

I'm planning on hooking up a low current cheap optoisolator/interrupter to
drive this transistor from the parallel port (albeit high voltage isolation)
so I have a good chance of not frying the computer if one of the motors
overheat or blows. Would this work for my application?

Any help would be appreciated.

http://rocky.digikey.com/WebLib/Fairchild/Web Data/TIP140_141_142.pdf

Thanks!

You might to get something like the 24 port controller card from
http://www.boondog.com/

VB3/VB6/C/PowerBasic source code: http://www.jecarter.com/programs.html
Freeware for the Palm with NS Basic source code: http://nsb.jecarter.com
Drivers for Pablo graphics tablet and JamCam cameras: http://home.earthlink.net/~mwbt/
johnecarter [email protected] mindspring dot.dot com. Fix the obvious to reply by email.

W

Watson A.Name - Watt Sun, Dark Remover

Jan 1, 1970
0
Hi,

Trying to control a 12V 5A motor from the parallel port. I have to control
ten of them, so I'm trying to get away without using expensive relays or
optoisolators ($20-$30 each). I found a monolithic darlington transistor
rated at 10 amps, already including reverse-current diodes and appropriate
resistors, perfect for my application (so it seems).

I'm planning on hooking up a low current cheap optoisolator/interrupter to
drive this transistor from the parallel port (albeit high voltage isolation)
so I have a good chance of not frying the computer if one of the motors
overheat or blows. Would this work for my application?

Any help would be appreciated.

I would use the circuit of Fig C in the following URL.
http://ourworld.compuserve.com/homepages/Bill_Bowden/r_ctrl.htm
But with the motor in place of the relay. This is similar to a
Darlingtom, but not the same, because the collectors are not tied
together. This is important to minimize the power dissipation of the
power transistor.

Also, remember that a relay is good for an isolator to keep the
voltages and currents on the contacts out of the PC. You can run
240VAC thru the contacts and not have to worry about it getting to the
PC side of the relay.

--
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goes directly to the trash unless you add NOSPAM in the
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W

Watson A.Name - Watt Sun, Dark Remover

Jan 1, 1970
0
Those darlingtons are marginal on their current capability. It is
true that under some conditions, they can stand a 10 ampere current,
but the gain curve that just makes it to 10 amperes specifies that
there is 4 volts across the device. Are you willing to have your 12
volt motor supply waste 4 volts across the transistor when the motor
draws 10 amperes? A motor rated for 5 ampere drain will allow quite a
bit more than 5 amperes pass during start up or stall. I would look
into finding a big MOSFET to do the switching. One with an on
resistance of less than (4 volts / 10 amperes)= 0.4 ohms would beat
the darlington. For example, the NDP603AL has an on resistance of
.022 ohms which would waste only .022*10=.22 volts during a 10 amp
surge. It is rated for 25 amps continuous duty, 100 amperes peak. It
sells for $.087 each if you order 10 from Digikey. That's not what I see. The Digikey prices show$8.70 for ten.

Even the mediocre IRF510 - which I believe is still avaiable at Radio
Scrap - would do a halfway decent job. And you could parallel two of
them. http://www.ee.nmt.edu/~wedeward/EE443L/FA99/IRF510.pdf
One other point... The diode that is internal to this device will not
protect the device during turn off. This protects the device from
applied reverse voltage. The motor produces a reverse voltage when it
is switched off, but this reverse voltage effectively adds to the 12
volt supply so as to increase the total voltage applied to the switch,
not reverse it. You will need additional diodes, one across each
motor, to clamp the reverse voltage they create. But the total energy
is pretty small (if the motor doesn't get forced to turn backwards) so
a 1 amp diode (1N4000) is probably plenty big.

A 1N4000 is a 7.5V zener diode, which would burn up as soon as the FET
turned on and applied 12V across it.

--
@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@,@@[email protected]@[email protected],@@[email protected]@[email protected]@[email protected]@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@

J

John Popelish

Jan 1, 1970
0
Watson A.Name - Watt Sun said:
That's not what I see. The Digikey prices show $8.70 for ten. Sorry. I intended to type$0.87 each...
Even the mediocre IRF510 - which I believe is still avaiable at Radio
Scrap - would do a halfway decent job. And you could parallel two of
them. http://www.ee.nmt.edu/~wedeward/EE443L/FA99/IRF510.pdf

A 1N4000 is a 7.5V zener diode, which would burn up as soon as the FET
turned on and applied 12V across it.

Thanks. That should be a 1N4001, 50 volt 1 amp diode. And this is
good enough only for on-off operation. If he is going to PWM the
motor, a 30 volt 5 amp schottky would be better.

M

Mike Beauchamp

Jan 1, 1970
0
I have used the Darlington array IC on a projecct I just did controlling
some 12V stepper motors with the Parallel Port. WOrked PERFECT!
There's some info on myy site if you click "pan/tilt webcam". good luck with
the project!

Mike
http://mikebeauchamp.com

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