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Need to multiply rev counter signal ?

G

George Gosbee

Jan 1, 1970
0
Hello all,

I'm after advice for a simple frequency multiplier, I need to increase the
rev counter signal on my car by 1.5 i.e. if revs are 2000 I need a signal of
3000. So it needs to be 12 vdc supply 0 - 7000 rpm input 0 - 11000 output.
Capable of easy build on a bit of Vero board.

Its to give the correct rev signal to a LPG system I have fitted but for
some reason it only reads 2/3 of the rev's. It may be something to do with
the fact that its a V6 working on a lost spark system. I.e. the plugs fire
every rev not just on the compression stroke.

TIA.

George.
 
J

John Fields

Jan 1, 1970
0
Hello all,

I'm after advice for a simple frequency multiplier, I need to increase the
rev counter signal on my car by 1.5 i.e. if revs are 2000 I need a signal of
3000. So it needs to be 12 vdc supply 0 - 7000 rpm input 0 - 11000 output.
Capable of easy build on a bit of Vero board.
 
G

George Gosbee

Jan 1, 1970
0
Thanks for the quick reply,

Its digital, and possibly a very spiky pulse. It is a wide ranging input, in
that it can get its signal from the HT coil primary or a wire wrapped around
one HT lead or the TDC sensor or the feed to the taco gauge.

George.
 
T

the Jackal

Jan 1, 1970
0
Hello all,

I'm after advice for a simple frequency multiplier, I need to increase the
rev counter signal on my car by 1.5 i.e. if revs are 2000 I need a signal of
3000. So it needs to be 12 vdc supply 0 - 7000 rpm input 0 - 11000 output.
Capable of easy build on a bit of Vero board.

Its to give the correct rev signal to a LPG system I have fitted but for
some reason it only reads 2/3 of the rev's. It may be something to do with
the fact that its a V6 working on a lost spark system. I.e. the plugs fire
every rev not just on the compression stroke.

TIA.

George.



Hello all,

I'm after advice for a simple frequency multiplier, I need to increase the
rev counter signal on my car by 1.5 i.e. if revs are 2000 I need a signal of
3000. So it needs to be 12 vdc supply 0 - 7000 rpm input 0 - 11000 output.
Capable of easy build on a bit of Vero board.

Its to give the correct rev signal to a LPG system I have fitted but for
some reason it only reads 2/3 of the rev's. It may be something to do with
the fact that its a V6 working on a lost spark system. I.e. the plugs fire
every rev not just on the compression stroke.

TIA.

George.
I'd say you have at least 3 alternatives to solving your problem :
1) Tougher way which though directly answers your question:
Transform a typical Class C single BJT/MOSFET amplifier circuit with
a parallel LC circuit at the collector/source.
Choose the L and C components such that LC tank resonates at 1.5f
where f is the frequency of your input signal.


2)Easier way.
There is probably a microcontroller that is counting the number of
revs from the engine shaft. You'll have to check for a DAC chip in
your tach that changes those engine pulses to an analog voltage. They
normally have an output pin where you can connect a pot to adjust the
output voltages. If the pot is already there everything is simpler, so
you'll avoid all the hassle of building up a seperate circuit to get
the job done, which would in any case be a simple circuit. You might
need the DACs datasheet to get that done.


3) Even more easier: Maybe next time....



theJackal
 
J

John Fields

Jan 1, 1970
0
Thanks for the quick reply,

Its digital, and possibly a very spiky pulse. It is a wide ranging input, in
that it can get its signal from the HT coil primary or a wire wrapped around
one HT lead or the TDC sensor or the feed to the taco gauge.

---
I'm confused. If you have so many input types available it seems
like there must be at least _one_ available which would fill the
bill. Does the possibility exist that you could change from the
signal source you're now using to another one which might work right
off the bat?

For example, the output from the TDC sensor gives you just one pulse
per revolution, which the interface might like a lot.

If you can't do it by selecting the signal source, then I can think
of two methods that might work, the first being to use your current
stream of pulses to fire a non-retriggerable one-shot with a small,
fixed period, then integrate those pulses and use the resultant DC
to drive a VCO which would, in turn, drive the interface.

The other way would be to use the input spikes to drive a
non-retriggerable one shot with a period of about half the time
between two input spikes at the highest speed at which the system is
supposed to work. Then use an EXOR with a delay on one of its
inputs to double the output frequency of the one shot, and a circuit
to remove every fourth EXOR output pulse. That way, for every 2
spikes in you'll get 3 EXOR output pulses out, which is what you
want, and if the interface is just counting pulses and time and
isn't worried about symmetry, then it'll probably work.

If you can't make it work by using another input source, and you
need a schematic, let me know, here, and I'll put something together
for you.
 
K

Ken Smith

Jan 1, 1970
0
Hello all,

I'm after advice for a simple frequency multiplier, I need to increase the
rev counter signal on my car by 1.5 i.e. if revs are 2000 I need a signal of
3000. So it needs to be 12 vdc supply 0 - 7000 rpm input 0 - 11000 output.
Capable of easy build on a bit of Vero board.

This sounds like a job for a CD4046.

You divide the frequency by 2 to feed one input of the phase detector-2
and the VCO by 3 to feed the other. Since an engine can't change RPM too
fast, it would be ok, I think.
 
K

Ken Smith

Jan 1, 1970
0
This sounds like a job for a CD4046.

You divide the frequency by 2 to feed one input of the phase detector-2
and the VCO by 3 to feed the other. Since an engine can't change RPM too
fast, it would be ok, I think.

Better yet, times three then divide by 2.
 
G

George Gosbee

Jan 1, 1970
0
Sounds good, will this chip need many discreet components? as you can guess
electronic design is not my profession.

I'm a HVAC controls man.

George.
 
K

Ken Smith

Jan 1, 1970
0
Sounds good, will this chip need many discreet components? as you can guess
electronic design is not my profession.
Go find at least a hobbiest electronics guy and suggest this to him:

-----------
! !
4046 part 4046 part ! ----- !
------- ----- -!D Q! !
in ---------! PD II !---/\/\/---+----! VCO !-------!> ! !
------- ! ----- ! Q/!-+--+-- Out
! --- R1 R2 C1 ----- !
! --- !
! ! C2 !
! GND !
! !
! ---------- !
--------------! Div by 3 !----------------
 
J

John Fields

Jan 1, 1970
0
-----------
! !
4046 part 4046 part ! ----- !
------- ----- -!D Q! !
in ---------! PD II !---/\/\/---+----! VCO !-------!> ! !
------- ! ----- ! Q/!-+--+-- Out
! --- R1 R2 C1 ----- !
! --- !
! ! C2 !
! GND !
! !
! ---------- !
--------------! Div by 3 !----------------
----------


---
Don't you mean:

-----------
! !
4046 part 4046 part ! ----- !
------- ----- -!D Q! !
in ---------! PD II !---/\/\/---+----! VCO !----+--!> ! !
------- ! ----- | ! Q/!----+--Out
! --- R1 R2 C1 | -----
! --- |
! ! C2 |
! GND |
! |
! ---------- |
--------------! Div by 3 !-----+
 
K

Ken Smith

Jan 1, 1970
0
---
Don't you mean:

-----------
! !
4046 part 4046 part ! ----- !
------- ----- -!D Q! !
in ---------! PD II !---/\/\/---+----! VCO !----+--!> ! !
------- ! ----- | ! Q/!----+--Out
! --- R1 R2 C1 | -----
! --- |
! ! C2 |
! GND |
! |
! ---------- |
--------------! Div by 3 !-----+
----------

Oooops yes!
 
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