Want to build a HEI ignition module similar to 70's style

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Does anyone have a schematic for a simple four pin HEI ignition module
from 1970's+ ignition systems. They appear to contain an SCR and a
pair of diodes and resistors.

Pickup Coil connects to two terminals and battery and induction coil
primary the other two, mounting screw provides a ground connection.

Original type mounted to the distributor plate on GM cars and others
and was ~1/4 round shape - I want to adapt it to a motorcycle that has
pickup coils mounted remote from the modules.

 

[Ross Herbert]

oes anyone have a schematic for a simple four pin HEI ignition module
:from 1970's+ ignition systems. They appear to contain an SCR and a
air of diodes and resistors.
:
ickup Coil connects to two terminals and battery and induction coil
rimary the other two, mounting screw provides a ground connection.
:
:Original type mounted to the distributor plate on GM cars and others
:and was ~1/4 round shape - I want to adapt it to a motorcycle that has
ickup coils mounted remote from the modules.


Most 70's era street bikes would run from the 12V battery supply so you would
have to buy a kit suitable for this power supply. I don't know where you are but
here is one kit http://www.jaycar.com.au/productView.asp?ID=KC5442

If your bike doesn't have a battery which is chaarged from an
alternator/generator then it will probably use an generator supply winding to
produce the input voltage. In this case a simpler kit can be used
http://www.jaycar.com.au/productView.asp?ID=KC5466

 

[neon]

if it contains an SCR then the 12 v must be increased to ~400v and the SCR discharges a capacitor charged to ~400v. that was for cars i have no idea about motorcycles ignition and coil pickup sorry.

 

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oes anyone have a schematic for a simple four pin HEI ignition module
:from 1970's+ ignition systems. They appear to contain an SCR and a
air of diodes and resistors.
:
ickup Coil connects to two terminals and battery and induction coil
rimary the other two, mounting screw provides a ground connection.
:
:Original type mounted to the distributor plate on GM cars and others
:and was ~1/4 round shape - I want to adapt it to a motorcycle that has
ickup coils mounted remote from the modules.

Most 70's era street bikes would run from the 12V battery supply so you would
have to buy a kit suitable for this power supply. I don't know where you are but
here is one kit http://www.jaycar.com.au/productView.asp?ID=KC5442

The bike is 80's runs from the battery. They call it a CDI but it
isn't - runs from 12V with no HT generator coil - the module just has
4-5 components in it (potted in black goo) induction coil is ~3.5
ohms.

The advance is managed in the pickup coil end of things.

The dealer wants $200 per module and I need two for a bike worth
~$1,000. The 70's style module for cars runs about $40 now (was $15)
each.

If your bike doesn't have a battery which is chaarged from an
alternator/generator then it will probably use an generator supply winding to
produce the input voltage. In this case a simpler kit can be used
http://www.jaycar.com.au/productView.asp?ID=KC5466

Physically too large even if it was suitable. The originals are only
one cubic inch with mostly heat sink.

turned this up in my searching
http://members.aol.com/pullingtractor/ignition.htm
Interesting site with lots of DIY mods for small gas engines.

 

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[snip]

Doesn't take much to make a CD Ignition, see....

http://analog-innovations.com/SED/CD-Ignition-Basic.pdf

Thanks. What is the theory of operation? What I have now, connects
one side of the coil to the battery and the other side to the ignition
module. In that circuit, D3 D2 would stay forward biased if the coil
goes to B+.

This circuit is supposed to dump a largish negative spike to the coil?

What kind of voltage does the transistor have to stand off?

 

[Tim Williams]

[snip]

Doesn't take much to make a CD Ignition, see....

http://analog-innovations.com/SED/CD-Ignition-Basic.pdf

Thanks.  What is the theory of operation?

Let's see, Q1 charges L1 thru D1, then when Q1 lets go, L1 charges C1
through D1 and D2. After a quarter sine wave, current reverses and
the diodes drop out, leaving C1 more or less charged inbetween
cycles. (Without D1, L1+C1 could oscillate, the current being carried
through D2 and D3; D1 produces a clean break after exactly a quarter
wave.) This puts a considerable voltage on Q1, something like, let's
see, 5A in 5mH is 62.5mJ so... about 353V. When the transistor turns
on again, C1 is discharged through D3 and the ignition coil, so it
will need to handle whatever the peak current is (Ice > 10A), and the
peak voltage (Vceo > 400V).

If possible, a 2ms one-shot should be used to charge the inductor,
since V = L * dI/dt --> 12V = 5mH * 5A/2ms. This circuit can repeat
as soon as the inductor is done whipping around, which takes about 0.1
ms.

The lynch pin of this circuit is the transistor, which must be quite
beefy. If nothing else, a stout base drive must be provided, which I
suppose isn't hard to do in an automotive environment. hFE = 5, if
not 3 or 2, is probably the kind of drive needed for a relatively high
Vce, ampy transistor in deep saturation. (Incidentially, t_stg will
probably end up something absurd like, 5us, 10us if you don't pull as
much current out of the base- but this delay isn't at all critical, as
long as t_f is reasonable, it won't burn up much switching power.
It's switching at audio frequencies after all.)

This circuit is supposed to dump a largish negative spike to the coil?

Yup!

Tim

 

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All of the control circuitry is not shown.

(1) Transistor turns on
(2) When current in inductor reaches 5A, transistor turns off, dumping
energy into capacitor (~350V)
(3) When transistor turns on again, capacitor dumps into ignition coil
(conventional ratio) firing plug; and inductor charging begins again.

Works great... I've used it to saw Plexiglas ;-)


I used 500V BVCEO (NPN) devices.

There are probably Power MOSFET's now that would work better... HV
NPN's have lousy beta, requiring beta correction circuits in the
current sensing.

...Jim Thompson

Thanks, I'll give it a try.

 

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Here's a link to the Delta Mark 10 CDI.
http://www.selectric.org/delta/index.html
I used to have a couple of these units back in the day... sure saved points and
plugs after I installed them. Never had a moment's trouble from either of
them... built both from kits.

--

Thanks. This isn't something I can use on this bike - too large. I
did build two of these myself in the 70's one went on a BMW motorcycle
and the other a Land Cruiser.

I think Jim's circuit is more viable given the components we have
today - and my size constraints. (although I could run one inverter
to boost voltage for both spark coils then just double up the SCR cap
circuits).

Appreciate the feedback, and I'll save the schematic

 

[default]

Thoughts coming back to me... with a conventional ignition coil (from
a car points-type system), peak primary current was 11 Amps! So size
your MOSFET accordingly.

Coil resistance is 3.5 ohms, that's only 4 amps.

 

[default]

When hit with 350V ?

...Jim Thompson

Oh.

 

[JosephKK]

Does anyone have a schematic for a simple four pin HEI ignition module
from 1970's+ ignition systems. They appear to contain an SCR and a
pair of diodes and resistors.

Pickup Coil connects to two terminals and battery and induction coil
primary the other two, mounting screw provides a ground connection.

Original type mounted to the distributor plate on GM cars and others
and was ~1/4 round shape - I want to adapt it to a motorcycle that has
pickup coils mounted remote from the modules.

Whatever you do, it will be specific to that make, model and year. Do
you know that most 4-cylinder MC have two ignition coils (and no
distributor)? (Some have 4, and many V-twins have two.) Many 1970s
and later MC have some variation of CDI already, do you know what it
currently has? What kind of sensor coils does it use (some still used
points)? Does it have speed variable timing, some do, and some don't.

 

[default]

Whatever you do, it will be specific to that make, model and year. Do
you know that most 4-cylinder MC have two ignition coils (and no
distributor)? (Some have 4, and many V-twins have two.) Many 1970s
and later MC have some variation of CDI already, do you know what it
currently has? What kind of sensor coils does it use (some still used
points)? Does it have speed variable timing, some do, and some don't.

Of course I know all that.

Make model and year - just a simple switch with no timing advance.

Duh? Like I haven't counted the coils by now? Two coils, two pickup
coils, four cylinders.

CDI is stretching a point - they call it CDI but the module is less
than a cubic inch - no room for a cap. Only one three terminal device
with no inductors, one tiny ceramic cap, and a few diodes - values
unknown. In the 80's CDI meant DC/DC converter and a box of ~10 cubic
inches charging up a 1 uf to 350V to discharge through an ignition
coil. This gizmo doesn't have that many parts - more like a
transistor switch goosed by a pickup coil as a magnet passes by,

No points - pickup coils.

No variable timing - that's done mechanically. Magnets are on a
centrifugal advanced plate, pickup coils are stationary.

It appears as if they just use a transistor switch. The coils have 12
volts to one side of the primary as long as the ignition is on.

When the motor is turning, the other side of the primary goes to
ground briefly. Two identical coils, two identical modules, each
alternately fires on each revolution of the crank - one wasted spark
per two cylinders.

I have an ignition module from a 1984 bike -same plug/receptacle but
the circuitry suggests there is an electronic advance using an RC
network - larger module, more parts, but it still works in the 1980
bike. Suggests to me that there is a primative advance circuit in the
module. But the 84 module still contains mostly passive components
with three small capacitors and more diodes and resistors.

Unlike outboard motors - the bike doesn't have a high voltage winding
on the charging circuit - everything works from 12 VDC.

 

[neon]

first thing you need it to boost 12 into ~400 v dc so you need a power oscillator that becomes the charge on a cap 1 mfd that is primary of your coil. now the points or the magnetics will fire the SCR to short the 400v cap causing a transfer to the secondary to 30-40kv enough to jump a spark plug. also the plug will not corode as fast because for every spark + will be some spark- replacing some metal if you use a 1 mfd charge cap then the power will be in the 100mw the spark plug should last for 50k miles. you can also remove the ovehang electrode because 40kv will spark the electrodes. it is an old design i must have biult 10 of them in the 70-80. IF YOU MAKE TOO HOT then the wires will leak and you will see corona all over the engine that is a bad idea.