Timing coil transistor output to transistor?

[amidis86]

Hello, i have a question, how can i on off an transistor using low ac voltage? or maybe there have another method ? I plan to get motorcycle timing signal from stator coil to trigger diy dc-cdi unit..

 

[amidis86]

would this circuit be ON the transistor when voltage on +, and OFF when -?

 

[duke37]

I do not understand what the circuit with 120V has to do with a motorcycle ignition circuit.
The transistor will be turning on when the base voltage is rising above 0.7V.
The transistor will be damaged when the voltage is negative, 5V reverse voltage is enough to keep the transistor off. To avoid the damage, put a diode across the base/emitter junction to limit the reverse voltage to 0.6V or so.

 

[john monks]

What is the voltage coming from your Stator coil?
I'm assuming your stator coil is part of a magneto.
Are you sure the phase angle is going to be correct?
Are you thinking about using your transistor in place of your pic16F84?
I assume it is going to be 300VAC at maximum. So I might suggest a diode as duke37 suggests and a small capacitor, maybe .001uF to help eliminate unwanted noise transients from triggering your ignition. I might suggest changing your transistor to a darlington arrangement. I would suggest leaving the transformer out of the circuit and using about 100Kohm 1watt pass resistor.
The transformer might saturate and it does add weight.

 

[amidis86]

Thank duke37 and john monks, sorry for false AC signal that i wrote, here my drawing. John, yes i want to used timing sensor as an input to cdi controller, using PIC16F628. May i know how the Darlington arrangement it is? I used 4N33, and simulated the opto output using LED, but fail to work.

Here my stator unit:

 

[john monks]

A darlington, more commonly called a darlington pair, is two transistors.
The collectors are connected together. The emitter of one is connected to the base of the other. Now you use device as a single transistor. The collectors as a collector, the unconnected base as the base and the unconnected emitter as the emitter.

The advantage is now you have a transistor with a super high amplification.
This allows you to drive the base with a very low base current and still have a very large change of collector current.

The new beta is beta times beta plus one.

I suggested this because you will want very little current feeding the resistor connected to the base to prevent the resistor from burning up.

 

[amidis86]

Here i try this few minute ago, the led blingking please correct me if there something wrong and need to fix back on this circuit..

 

[Rleo6965]

Much better if you can provide voltage output of your timing sensor. This will help design or compute component to amplify the timing sensor signal for scr triggering.

 

[john monks]

Would be better if the diode was placed between the base of the transistor and ground.
The 4.7K resistor probably should be about 100kohm 1 watt. A 4.7K will get to hot (about 19 watts).
You might need a small capacitor from the base of the transistor to ground to prevent spurious pulses from triggering your ignition.

Other than that looks good.
You might want to measure the voltage coming from your stator coil.
The power dissipated by the resistor is voltage squared divided by the resistance.

 

[amidis86]

Thank Rleo6965 and john monks, here the modification circuit..

http://s13.postimage.org/ceqorcqw7/Supp8.jpg

here i putting multimeter to 200ac range and the voltage come out from timing senso is like below :

on idle 00.2vac
on full throttle gear 2-3 i got 01.8vac
on full throttle gear 4 i got 01.5-01.6vac

 

[Rleo6965]

Oops. You placed 1N4007 in wrong polarity. Any signals passing 1N4148 will be directly pass to 1N4007 to ground. Might as well removed 1N4007 and circuit will still work. Also change value of 100K resistor into 1K. That 100k was to much for 1.6V timing sensor output voltage and might not enough to drive the base of darlington circuit. Also place 4.7K resistor on collector of transistor and connect to +5V. This will act as pullup resistor giving PIC very good input signal.

You need oscilloscope to accurately measure output of Timing Sensor. Google on your Timing Sensor so you can get datasheet and get those information you need.

 

[amidis86]

Hello, sorry for the late, i just done some school assigment , i dont have any oscilloscipe, but can i used pocket DSO oscilloscope on ebay, i can order one if it work? I cannot find any datasheet about timing sensor, because it stock from factory. Only part number and motorcycle model available.

http://www.ebay.com/itm/ARM-DSO201-...85541?pt=BI_Oscilloscopes&hash=item1e72937625

 

[Rleo6965]

That scope will be suitable for testing your project and save you lot of time to finish it. Buy extra X10 probe. So that you will able to test the primary coil of ignition coil which maybe around 200V PP. ( DO NOT USE TO TEST THE SECONDARY HIGH VOLTAGE).

I hope I have that scope when I'm building my own multispark cdis. Because I have to use my cellphone camera to capture elusive pulses from my 20 yrs old Leader 1021 for analysis.
That DSO201M had memory function that really help analyzing fast pulses. The good part was you can upload those captured data to your computer for better viewing.

My CDIS project was now functional and now installed in my Mitsubishi Lancer since last April this year 2012.

 

[amidis86]

Thank Rleo6965, i just order the osc ;D,"My CDIS project was now functional and now installed in my Mitsubishi Lancer since last April this year 2012," it is open source or you sell it? Can you upload some video on youtube ? like to see your CDIS..it cool

 

[amidis86]

May i know what we call the signal to the pic? On pic side it will be counter function or analog input? I need some correct keyword for this function..

 

[Rleo6965]

Here is the video of my Multispark CDIS under test,

Picture of my prototype CDIS installed in my Mitsubishi Lancer EL 1996 using Distributor Transducer as trigger signal source.

Note : Distributor Assembly wire was modified to adapt with CDIS ( right side of picture )
Designed connectors wiring for easy revert to original stock wiring of car ignition system. Plug and Play. No tools required.

 

[Rleo6965]

Planning to sell my Multispark CDIS but I still have not enough budget to mass produce it. Already created smaller pcb 5"X3" footprint for smaller aluminum casing.

Please see your original diagram. I add 2 resistor to your circuit. Hope this help.

Any news of your new oscilloscope? Planning to buy one in the future.

 

[duke37]

I have not been following this thread but the resulting circuit seems rather strange.
You have a diddy 1N4148 feeding in and a fat 1N4007 inside the circuit. Why?

What does the 1N4007 do? The input diode stops any negative voltage. If you do wish to have extra protection to the Darlington from negative input, the 1N4007 diode should be adjacent to it.