Diesel tacho circuit

[newbie19]

Hello Friends,

I am a newbie to electronics . I want to understand the tacho circuit as shown in the figure. I figured out that this circuit uses CS8190 air core driver. I don't understand input circuit and the OPAMP circuit. This circuit uses OPAMP (LM324N) as buffer to drive CS8190 using external DC voltage . It also uses the LM2907 which converts the input frequency to voltage which i believe feeds the CS8190 through opamp. How ever i have the hard time understanding in detail the opamp & 2907 circuit.

Any help will be appereciated.

Thanks in advance !!

 

[Bluejets]

If you replace the ic symbols with their actual circuit equivalents, it may appear clearer.
You answered your own question with the lm2907.

 

[AnalogKid]

Where did you get this schematic. Not to pile on, but package outlines usually make a schematic worse, not better.

A schematic tells the story of the electrical (*not* physical) relationships among the components, signals, and power supplies. Signals flow from left to right, power from top to bottom. And ground symbols *always* point down.

There are far too many 14 pin components to assume that an unknown viewer will carry around in his head the exact pinout for your components. This is especially true for compound components such as quad opamps and gates. Consider that TTL and CMOS quad NAND gates have very different pinouts, as do the closely related (and sometimes interchangeable) LM324 and LM339.

ak

 

[newbie19]

Where did you get this schematic. Not to pile on, but package outlines usually make a schematic worse, not better.

A schematic tells the story of the electrical (*not* physical) relationships among the components, signals, and power supplies. Signals flow from left to right, power from top to bottom. And ground symbols *always* point down.

There are far too many 14 pin components to assume that an unknown viewer will carry around in his head the exact pinout for your components. This is especially true for compound components such as quad opamps and gates. Consider that TTL and CMOS quad NAND gates have very different pinouts, as do the closely related (and sometimes interchangeable) LM324 and LM339.

ak

thanks For the reply. you are right that it is difficult for the viewer to carry exact pinout of the Components. I am just trying to figure out what is the purpose of the devices used in combination to have a bigger picture. and then i will look into details. This is a drawing of a diesel tachometer designed by someone previously at my work. I am trying to figure out the purpose of each component and basic understanding about it ( Again not reached to the point to study in detail) . As i already said that i am a beginner.

 

[newbie19]

If you replace the ic symbols with their actual circuit equivalents, it may appear clearer.
You answered your own question with the lm2907.

thanks for the reply. I will try to replace the IC symbol with the actual circuit and move on from there .
my question is the why the voltage to frequency converter ( LM2907) is not directly fed to CS8190. Why do it feeds OPAMP which in turn outputs to CS8190.

Is it the to match impedance or add gain to output ?

as said i will replace the internal circuit of IC & will make more primitive circuit diagram and study further. I already started and found little information that it uses one of the Quad OPAMP as comparator which have Frequency input to non-inverting input and a voltage divider ( 1k / (1k + 10k) ) with the 10v input fed to Inverting input of OPAMP and the output is fed to Pin-1 of (LM2907). that is pretty clear what happens there.

 

[AnalogKid]

i am a beginner.

Then I think an excellent starting exercise is to redraw the opamp and F/V sections of the schematic using the correct symbols and post it. You will gain a much better understanding of the signals, and we will be much more willing to assist.

ak

 

[newbie19]

Then I think an excellent starting exercise is to redraw the opamp and F/V sections of the schematic using the correct symbols and post it. You will gain a much better understanding of the signals, and we will be much more willing to assist.

ak

Thanks AnalogKid for the feedback.

This is the New Schematic which I made breaking down the IC pinouts.
Now can you Please enlighten what is happening here .