so 12vdc and then 6vdc on trigger coil and i should see 12v output on wire from cdi to ignition coil?

You would see 0V, pulsing very briefly to -12V. To see +12V you would need access to both terminals of the capacitor (not possible if the CDI is a sealed/potted unit).

ok, i can use 230v ac from wall

Not directly; that would be dangerous. Use an isolation transformer and a resistor to limit its output current. 230VAC has a peak voltage of 325V, so you would need to know that the capacitor is rated for at least that voltage.

 

i have ac transformer that give 180vac, so any idea how to do this test? from transformer one wire to cdi that normally is connected to charge coil in engine, and second wire 0 to the ground wire of cdi? that should charge capacitor inside cdi yes?

 

You would need a resistor in series with the transformer secondary winding; otherwise when the SCR fires, that winding would be practically short-circuited. 180V must be treated with respect. Even when it comes from an isolation transformer it can be LETHAL.
Does that transformer have a lower voltage winding as well as the 180V one?
I've seen various CDI circuits on the net. Do you know what voltage and pulse duration are used for triggering your particular CDI unit, or are you just guessing 6V?
Are you intending to test more than one type of CDI unit?

 

i have about 6 windings, the lowest is about 60-70v can you draw some schematic how it should be connected?

 

I would need to know the trigger coil voltage range and SCR gate current used in your CDI before drawing a schematic. I was thinking a low voltage secondary winding could be used for the triggering, but 60-70V seems too high. You don't want your test to be a test-to-destruction .

 

i have few el cheapo cdi from china scooters, most of time they use 2p4m scr , most of time trigger voltage are from 4-14v depends of engine. we cant use dc for triggering?

 

i have few el cheapo cdi from china scooters, most of time they use 2p4m scr , most of time trigger voltage are from 4-14v depends of engine. we cant use dc for triggering?

A DC voltage will keep the SCR triggered and short the HV supply output until the DC is removed.

 

You could use DC, but then the DC polarity is a factor. For example, if the CDI is like one of these, the required trigger pulse polarity would be negative with respect to the ground line. Also, for the 2P4M SCR the maximum reverse gate voltage is 6V, so you would have to be careful not to exceed that if the CDI has no reverse-voltage protection built in.

 

ok so to not damage scr i must not exceed reverse gate voltage, and not exceed gate current?

 

ok so to not damage scr i must not exceed reverse gate voltage, and not exceed gate current?

That would appear to be a no-brainer.
That's the reason for those Absolute Maximum ratings in the data sheet.

 

ok, then i must know how many A trigger coil produce and then calculate resistor?

 

I'm not a petrol-head, but from my limited googling it seems each manufacturer has their own idea of what goes into a CDI. Some, for example, apparently include automatic timing advance circuitry. Some are 4-wire, some are 5-wire. This makes it difficult to design a universal tester.
Do you have a datasheet, or any data in fact, for your particular CDI? Unless you know the maximum inputs your CDI can tolerate you risk damaging it, and unless you know the minimum inputs it requires for satisfactory operation your test result won't be reliable.

 

i have specification for almost all brand of engines most of them are 150v minimum for charging, and 0.6v to 12v for trigger so i the 150v is minimal value so this will can be use for all, and for trigger i must somehow have source of ac that i can set 0.6v ,6v ,12v

 

i found few transformer in house but one output 8v second 2v third one 21v, is any way to lower output voltages of transformer ? idk maybe using resistors?

 

Since the trigger current is likely to be fairly small (<20mA, for a guess), it would be practical to use resistors to make one or more voltage dividers.

i found few transformer in house but one output 8v second 2v third one 21v

Could be useful, providing those 'transformers' output AC voltages and aren't actually DC power supplies.
BTW, I've just come across this CDI tester schematic, which may be of interest. It's a reminder that some CDIs use a 12VDC input rather than HV AC input.

 

ok, i have 2 transformer one lets say output 80vac and it will be charging capacitor, second transformer output 6v and it will be trigger scr, but cdi have only one ground wire, how to know what wire from transformer are ground , since i must connect 2 ground wires from transformer to have one ground

 

Have you confirmed that the 6V 'transformer' has an AC output, not DC? For any AC output it doesn't matter which wire is connected to the ground point.

 

yes its straight from transformer wires so it cant be dc

 

Alec_t possible to get your @ ?

 

I prefer to keep things in the public forum.