Speed-limit Alert PLEASE HELP!!!!!!!!

[audioguru2]

Oh yeah,
1000uF across the car battery and 470uF across the circuit will filter out alternator whine and things that turn on and off like turn signals very well. I have some 1000uF capacitors that are quite inexpensive and are small.

 

[Mandavar]

Hi Audiogurur
As i know the signal we want to sense its over/under frequency is the signal we obtain from pin 12 of IC2 and connected to pin 1 of (LM2917) my question why Connected pin 11 of (Lm2917) to the end of R5? What is the signal we obtain from the end of R5?

 

[audioguru2]

R4 and R5 have equal values and are in series across the supply. Their junction is a DC voltage that is half the supply voltage and is used as the DC reference voltage for opamp IC1 and for the opamp at pin 11 of the LM2917. The output of the parallel inverters is also about half the supply voltage and is connected to the pin 1 input of the opamp in the LM2917 so it can amplify the signal very well.

 

[Mandavar]

Hi Audiogurur
I have another question about the Capacitor C2 that is connected to IC2A which has a feedback R7 does this makes IC2A a Diffrentiator and if yes what is the need of it?

And another thing about capacitor C1 What is the main purpose of it?

Really thanks for your help you are so helpfull

Have a nice day

 

[audioguru2]

I think C2 is to prevent the DC at the output of IC1 from affecting the input DC voltage of IC2.

C1 is just a filter for the DC reference voltage.

 

[Mandavar]

Hi Audioguru
you told me before that the capacitors can filter out alternator whine and some nosie .. i just wonder how can capacitor do that? and does the filtration improves when we increase the capacitor value? i just want to know the realtion between the capacitors and the filtering thing and how it works..

Thanks for your help again

 

[audioguru2]

Hi Mandavar,
A properly designed and connected car amplifier does not reproduce alternator whine.
Its high gain circuit should be supplied with a filtered DC supply voltage. The filter is a resistor in series then a capacitor to ground at the amplifier's high gain circuit.

A capacitor has "reactance" which is its impedance that depends on its value and on the frequency. A high value or a high frequency will attenuate the interfering frequency better.

 

[Mandavar]

Hi Audioguru
I have a questions about IC1 (Diffrential amplifier) ..
Is the same signal picked up by the sensor coil (inductor) entering the inverting and the non-inverting inputs of the IC1 if yes why is that?
and in what mode this Diffrential amplifier is working (Common-mode??) ?

 

[audioguru2]

The sensor coil develops a small voltage across it when it picks up a signal.
The inputs of a differential amplifier are opposites. A signal between them is differential and is amplified. The voltage from the sensor coil is between the inputs.
The same common-mode signal (interference) to both inputs is cancelled.

 

[Mandavar]

Hi Audioguru
What effect does R7 do? why its used?
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How can we describe by equations the voltage at Pin 2 & Pin3 of IC1 (Diffrential amplifier)
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Thanks for ur help

 

[audioguru2]

What effect does R7 do? why its used?

R7 biases the inverter IC2A into the linear region so it acts like a high gain linear amplifier.

How can we describe by equations the voltage at Pin 2 & Pin3 of IC1 (Diffrential amplifier)

Google has the equations. The gain is the ratio of the feedback resistors.

 

[Mandavar]

Hi Audioguru
in the operation description of this project the author write down that IC2B To IC2F (Cmos Inveters) do a clean pluse squaring to the signal. my qustion is how by inverting a signal we can have a clean pluse squaring operation?
And does these inverters further amplifiy the signal besides the inverting?
Thanks for your help again

 

[audioguru2]

in the operation description of this project the author write down that IC2B To IC2F (Cmos Inveters) do a clean pluse squaring to the signal. my qustion is how by inverting a signal we can have a clean pluse squaring operation?
And does these inverters further amplifiy the signal besides the inverting?

A Cmos inverter has a gain of about 30 with a 9V supply voltage. This circuit has 4 0f them cascaded so their total gain is about 810,000 so a tiny signal at the input causes the last few inverters to produce clean saturated square-waves.
Here is a graph showing that the gain of a Cmos inverter depends on its supply voltage:
View attachment 40320

 

[theglobe]

How can i modify the speed-limit alert circuit by using the speedometer itself as a sensor instead of using the miniature inductor???