auto mobile cd70 circuit need help

[easy electronics]

This is a circuit pulled from honda bike.
i want to know about what is the working of this circuit and components .

there is a microcontroller PIC12C508A & mn638s

 

[milan.rajik]

Hero Honda bike ? Such a low quality board with low quality components. They have to be awarded for manufacturing low quality products for the bike.

The big 3 pin device seems like power regulator. Maybe to provide 5V power for microcontroller circuits used in digital speedometers etc...

 

[kam1787]

Looks like a 2nd level sporadic chronic cross integrator with tertiary bypass across the 3rd pole of reactant controller
visually the internal rom with a complex set gives a relationship eigenvalue with discontinuity at the delta v over 3rdquadrant

 

[milan.rajik]

How do you say that ? Did you checked the part number of the devices ? I just made a guess.

 

[betwixt]

The 'big' black thing is a darlington power transistor, the little black thing is a microcontroller.
What it does is anyones guess. With it removed, what doesn't work on the bike?
The transistor is rated at over 300V so I would guess it's part of a capacitor discharge ignition unit.

Kam1787, you didn't mention the kafuffle clamp diode or the crossflow wimwom damper. Without them it can go 'critical' at any time.

Brian.

 

[milan.rajik]

The little black thing can't be a MCU because MCU needs more connection in the buy circuitry. It has to display speedometer value, fuel level, monitor ignition system and other things. Maybe my guess was wrong but I could not see the part numbers clearly.

Is it M on the little black chip ? It looks to me like microchip symbol M.

 

[betwixt]

It is an 'M' for Microchip. It's a 12C508A microcontroller. My guess it it works to operate the ignition advance in a CD ignition system. If I'm right, it would receive a pulse from a pickup on the flywheel and pass it to the transistor to generate the spark. As the speed increases, it would turn the transistor on slightly earlier to advance the spark timing and increase engine efficiency.

The CD70 is a relatively old and cheap motorcycle but it did have CDI. The speedometer was mechanical and the fuel level was checked by shaking the bike and listening to how much splash you could hear. :lol:

Brian.

 

[milan.rajik]

Yes, you are right it is PIC12C. I have never used the C type device only F type and hence it doesn't come to my mind.

 

[betwixt]

'C' and their 'F' replacements are almost the same. 'F' for Flash is cheaper to manufacture and in most cases makes the devices reprogrammable but the PIC used (and it's 'F' version) are still very popular in low demand applications.

Brian.

 

[easy electronics]

what is result of your discussion .
i have understand only one thing with your discussion .
Q. how to check fuel level in bike .
Ans." shaking the bike and listening to how much splash you could hear"

 

[milan.rajik]

@easy electronics

To get better answers you have to atleast tell what is the name of that automobile product and what wires or other units connect to the device. Like if it connects to ignition unit or any other unit.

 

[easy electronics]

sorry for my wrong knowledge about this circuit .

i have checked and found that
this circuit is a part of Car electrical system .

this is this kind of circuit .
https://www.google.com.pk/search?q=hot+spark+ignition+kit&biw=1280&bih=699&source=lnms&tbm=isch&sa=X&ei=k5jTVPiDOsz5ULv7g7AP&ved=0CAYQ_AUoAQ#tbm=isch&q=hot+spark+ignition+kit+distribution+cd

 

[betwixt]

It still doesn't help us, that link is to a page full of ignition units.

I still say my best GUESS is it's the firing circuit of a CD ignition unit. There is another possibility that might apply in the case of a car, a light dimming unit. Some cars have dimmed headlight or interior control that uses PWM to limit the light power, it's an efficient way of doing it. However, it would seem inappropriate to use a 300V transistor in a circuit running off no more than 12V so I think it relatively unlikely that is it's purpose.

The small IC is a microcontroller, it's a generic part that has to be programmed to do a specific job. That's what makes it difficult to tell what it does, it's whole functionality depends on the program it runs so without knowing how it connects to the rest of the wiring it could be doing almost anything.

Think of your problem this way: if I handed you a remote control unit that had no marking on the buttons and no manufacturers name on it, would you be able to tell what equipment it operated and what each of the buttons did? It might be obvious it's a remote control unit but it could be for an air conditioning unit, a DVD player, open a garage door or operate factory lights.

Brian.

 

[easy electronics]

well it is car circuit to generate spark.
it has a read switch connected with it and when read switch find any pulse it generates spark .
now i want to know about circuit.

 

[betwixt]

We already told you. It picks up the signal from the 'reed switch' which is probably really a reluctance sensor, it uses the signal to turn the transistor on, the transistor current energizes the ignition coil and when the transistor turns off, the coil generates a spark. The little IC is there to set how long the transistor is turned on for and when it turns on relative to the signal from the sensor.

It is a custom made part, if you want a schematic you will have to contact the car manufacturer or trace it out yourself. I doubt they will give it you because it is proprietary information. The exact function of the IC depends on the program inside it. It is a small self-contained computer which does what it's program tells it. That type has a copy protection mechanism that stops you reading the code from it so there is no chance of 'reverse engineering' it to reveal it's instructions.

Brian.