Transistor assisted Ignition

  • Thread starter Jack Jet Williams
  • Start date
J

Jack Jet Williams

Guest
Would someone PLEASE tell me how to wire a transistor to fire a
ignition coil so the breaker points do not wear out so fast ? I have
looked for circuit diagrams but have not found any.........Someone
please help me.

Thanks.

Jack Jet Williams
Hesperia,Ca.
 
"Jack Jet Williams" <jackjet@gte.net> wrote in message
news:810207e1.0312040723.74673627@posting.google.com...
Would someone PLEASE tell me how to wire a transistor to fire a
ignition coil so the breaker points do not wear out so fast ? I have
looked for circuit diagrams but have not found any.........Someone
please help me.
Click to expand...
The transistor is used as a switch, in the place of the contacts. The
contacts would never have to be used, unless you decide to use them at low
voltage to provide the sensing signal that tells the transistor when to fire.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
 
"Sir Charles W. Shults III" <aichipREM@OVEcfl.THISrr.com> wrote in message news:<LqJzb.22519$%h4.20712@twister.tampabay.rr.com>...
"Jack Jet Williams" <jackjet@gte.net> wrote in message
news:810207e1.0312040723.74673627@posting.google.com...
Would someone PLEASE tell me how to wire a transistor to fire a
ignition coil so the breaker points do not wear out so fast ? I have
looked for circuit diagrams but have not found any.........Someone
please help me.

The transistor is used as a switch, in the place of the contacts. The
contacts would never have to be used, unless you decide to use them at low
voltage to provide the sensing signal that tells the transistor when to fire.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
Click to expand...
Hi Chip,
thanks - what I want to do is install this circuit on my 1974
Honda 750 motorcycle - the points burn and pit pretty quickly - I know
that a transistor could switch the the coils - then the current across
the points would be in the milliamp range - and they would last for a
long time - instead of the 8 amps. now across them.........how do you
connect the transistor to the points ?

Thanks.
Jack Jet Williams
 
Would someone PLEASE tell me how to wire a transistor to fire a
ignition coil so the breaker points do not wear out so fast ? I have
looked for circuit diagrams but have not found any.........Someone
please help me.

The transistor is used as a switch, in the place of the contacts.
The
contacts would never have to be used, unless you decide to use them at
low
voltage to provide the sensing signal that tells the transistor when to
fire. Cheers! Chip Shults
Click to expand...

Hi Chip,
thanks - what I want to do is install this circuit on my 1974
Honda 750 motorcycle - the points burn and pit pretty quickly - I know
that a transistor could switch the the coils - then the current across
the points would be in the milliamp range - and they would last for a
long time - instead of the 8 amps. now across them.........how do you
connect the transistor to the points ?
Thanks.
Jack Jet Williams
Click to expand...
Do you have the module? What type? Most newer ICM triggers a spark when
grounding the input. Older ones when releasing (removing) ground. Use ICM
(ignition control modules, aka igniter) as they range from tiny to large
ones at the salvage yard. Unlike transistors, they limit current (lengthen
coil's life) and produce sufficient current each cyle.

The induced voltage is also determined by the rate of collapse, which is
determined by the speed of the switching of the earth path. Another words,
you will notice a bigger spark using the ICM.

The bottom picture, figure 1, is a good replica block circuit of the
reliable NEC for Honda ICM.- reluctor controlled. This one produce a spark
when S1 is cut short of ground. S2 is left empty.

http://autotails.tripod.com/ignition.htm

Below is a picture, no internal circuit, of a 90's ICM computer triggerred.

http://autotails.tripod.com/rov-rgn0.gif

This one is a Toyota, computer triggered, block circuit.

http://autotails.tripod.com/s.gif

Indi
 
The points typically ground something (like the coil) when they close. This
is the key- use a transistor that switches on when its base is taken low. A PNP
bipolar power transistor would be a good solution.
Connect the base of the transistor to two resistors- one is a fairly high
value one, like 2.7 K and goes to the 12 volt supply. The other is perhaps 120
ohms and goes to the contacts. What will happen is this. As the contacts are
in the open state, the base is pulled to the 12 volt side and the transistor is
turned off. When the contacts close, the base is drawn to the low side (ground)
and the transistor switches on.
Now, the emitter of the transistor will be connected to the coil to be
driven, and the collector will be connected to ground. It is a good practice to
place a series resistor (like 1 or 2 ohms) in series with the emitter to keep
the current limited.
The coil, incidentally, is an inductive device and will likely blow out a
transistor the first time you fire it this way. The solution is to place a
diode (sometimes referred to as a "snubber") in parallel with the transistor-
across the emitter and collector.
Use a fast rectifier for the diode and wire the cathode directly to the
transistor's emitter. The anode of the diode will go to the collector.
This will give you a circuit to play around with and see how it will work
for your application.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
 
"Sir Charles W. Shults III" <aichipREM@OVEcfl.THISrr.com> wrote in message news:<itqAb.30629$%h4.13407@twister.tampabay.rr.com>...
The points typically ground something (like the coil) when they close. This
is the key- use a transistor that switches on when its base is taken low. A PNP
bipolar power transistor would be a good solution.
Connect the base of the transistor to two resistors- one is a fairly high
value one, like 2.7 K and goes to the 12 volt supply. The other is perhaps 120
ohms and goes to the contacts. What will happen is this. As the contacts are
in the open state, the base is pulled to the 12 volt side and the transistor is
turned off. When the contacts close, the base is drawn to the low side (ground)
and the transistor switches on.
Now, the emitter of the transistor will be connected to the coil to be
driven, and the collector will be connected to ground. It is a good practice to
place a series resistor (like 1 or 2 ohms) in series with the emitter to keep
the current limited.
The coil, incidentally, is an inductive device and will likely blow out a
transistor the first time you fire it this way. The solution is to place a
diode (sometimes referred to as a "snubber") in parallel with the transistor-
across the emitter and collector.
Use a fast rectifier for the diode and wire the cathode directly to the
transistor's emitter. The anode of the diode will go to the collector.
This will give you a circuit to play around with and see how it will work
for your application.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
Click to expand...
Thanks Chip ,

This 750 Honda is a 1974 model - it has no electronic module at all
- the
points are wired in series with the coil- and a capsaitor(did I spell
that right?) is across the points - VERY simple - thanks for telling
me how to do this with a transistor.

Jack Jet Williams
Hesperia,Ca.
 
Your braker points are wearing out because of capacitor.It.s maybe to small
or it's not functioning.Place the new one(it should be 0.25uF).It's not
smart to use PNP tanzistors.There are many NPN transistors made especialy
for car ignition systems(with build-in protection against spikes made by
coil).Some of them are:BU323, BU920, BU921, BU922, BUV37B (TOP3), BUW29,
BUW81, BUX37, MJ10012, MJ10013, MJ10014, TIP662, TIP665, 2SD683, 2SD685.
The transistorised ignition need to be made very good,need to be
waterproof,sealed.If it's not build propery it can brought you many
troubles.



"Jack Jet Williams" <jackjet@gte.net> wrote in message
news:810207e1.0312082330.30e606de@posting.google.com...
"Sir Charles W. Shults III" <aichipREM@OVEcfl.THISrr.com> wrote in message
news:<itqAb.30629$%h4.13407@twister.tampabay.rr.com>...
The points typically ground something (like the coil) when they close.
This
is the key- use a transistor that switches on when its base is taken
low. A PNP
bipolar power transistor would be a good solution.
Connect the base of the transistor to two resistors- one is a fairly
high
value one, like 2.7 K and goes to the 12 volt supply. The other is
perhaps 120
ohms and goes to the contacts. What will happen is this. As the
contacts are
in the open state, the base is pulled to the 12 volt side and the
transistor is
turned off. When the contacts close, the base is drawn to the low side
(ground)
and the transistor switches on.
Now, the emitter of the transistor will be connected to the coil to
be
driven, and the collector will be connected to ground. It is a good
practice to
place a series resistor (like 1 or 2 ohms) in series with the emitter to
keep
the current limited.
The coil, incidentally, is an inductive device and will likely blow
out a
transistor the first time you fire it this way. The solution is to
place a
diode (sometimes referred to as a "snubber") in parallel with the
transistor-
across the emitter and collector.
Use a fast rectifier for the diode and wire the cathode directly to
the
transistor's emitter. The anode of the diode will go to the collector.
This will give you a circuit to play around with and see how it will
work
for your application.

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

Thanks Chip ,

This 750 Honda is a 1974 model - it has no electronic module at all
- the
points are wired in series with the coil- and a capsaitor(did I spell
that right?) is across the points - VERY simple - thanks for telling
me how to do this with a transistor.

Jack Jet Williams
Hesperia,Ca.
Click to expand...
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top