Hello, anyone have some simlpe idea to build some test bench for ac cdi? i know i must supply ac to charge capacitor and then give low voltage signal to scr to release power from capacitor, to hv coil, most of the time, cdi have one wire for hv coil , one wire to charging capacitor, and one input wire from trigger coil, so trigger and ignition coil use the same ground

 

Welcome to AAC!
Googling "cdi schematic" should get you started.

 

yes but i want device to test cdi not to build cdi

 

In order to test a CDI (other than merely seeing if it does/doesn't work) you need to understand what it consists of. For this, a schematic is the best starting point. A multimeter would then be useful to identify possible fault causes.
Do you want to merely do a simple go/no-go test, or something more elaborate involving current/voltage/timing parameters?

 

simple tester to check if cdi output spark, i know how cdi works and how its build, i must supply ac to two wire to chagre capastitor, and suply ac lower voltage about 5-10v to 2 wire to trigger thyristor to release voltage cumulated in capacitor.

 

simple tester to check if cdi output spark

Is this a bench test?
Why not just use a sparkplug at the output and observe whether there's a spark?

To avoid this turning into another 20-question thread, please state exactly what device you are testing (other than saying it's a CDI) and how to you want to perform the test, since that is not at all clear.

 

yes i want test bench to checking cdi without engine. to see if cdi work, i must charge capacitor inside of cdi, and then supply small voltage to thyristor to release voltage from capacitor to wire that go to hv coil. i think all must be done via ac ? since engine produce ac voltage. idk how to say it easier. i need to buuild something that i connect cdi and i can check if cdi work properly giving voltage after triggering thyristor

 

I need to see the complete circuit, including how the capacitor is charged by the engine.

 

 

Good.

Do you know what the output of the exciter coil is?

So show exactly how much of the circuit you want to test on the bench.

 

depends, but lets say 200v

 

lets say 200v

Even at low rpm? I would have expected much lower than 200V in a worst case scenario when trying to get an engine started.
Is the ignition coil part of the CDI unit or external to it?

 

i dont want to simulate engine, i just want to know if cdi is working , so i supply 200v and trigger and then measure if i get 200v output.

 

i dont want to simulate engine, i just want to know if cdi is working , so i supply 200v and trigger and then measure if i get 200v output.

I think it would be better to add a coil and sparkplug to the setup so you could see if it properly generates an output spark.
Just about any old ignition coil should work for that.

An the voltage should be from an AC source so that the diode is checked also.

 

i dont want to simulate engine

I wasn't suggesting that. A faulty CDI (e.g with a leaky capacitor) fed with 200VAC might well 'work', but perhaps it wouldn't if fed with a lower voltage such as the exciter coil would generate at low rpm (during engine start, or tick-over). Your test should allow for both minimum and maximum input voltages.

 

ok, if i apply 12vdc like on picture, and then measure on blue lines i should see about 11-12v right? so if i apply 12v, capacitor should charge to 12v, and then when i apply small voltage like 3-5V on trigger then scr should release 12v stored in capacitor right?

 

so if i apply 12v, capacitor should charge to 12v

If there are no leaky components, 12VAC (RMS) at the exciter coil terminals would provide nearly 12 x √2 ≅ 16.5VDC across the capacitor. Where your top probe is positioned the voltage would be zero until the SCR fired. There would then be a brief negative pulse and oscillation (too brief for most multimeters to give a useful reading, but viewable on an oscilloscope) whose amplitude and frequency would depend on the ignition coil's properties and on the capacitor value.
You could use current-limited DC voltages in place of the usual AC exciter and trigger inputs.

 

look careful i said i use 12v dc, not ac, not to simulate engine, but only to see if cdi works, so 12vdc and then 6vdc on trigger coil and i should see 12v output on wire from cdi to ignition coil?

 

look careful i said i use 12v dc, not ac, not to simulate engine, but only to see if cdi works, so 12vdc and then 6vdc on trigger coil and i should see 12v output on wire from cdi to ignition coil?

That would not verify if the diode is working properly, or whether the circuit can tolerate its normal working voltage.

 

ok, i can use 230v ac from wall , anyone have any idea how this test device should work to test cdi