Sure wish I had this when I was a mechanic's instructor. This is one of the most concise, well conceived and presented little video "vignettes" on this subject I have ever seen. WELL DONE SIR! Thank YOU!
Thanks Daniel, I've been busy working on a 50,000 Watt transmitter. Both three-phase circuit breakers failed. The station was off the air since Wednesday afternoon, got the parts in today and she's back on the air. Glad the video was helpful. Rick
I would like to add a note here, because it seems some people having trouble understanding it. Not all cdi's have this excitor coil, some old cdi's have that. Most of them nowdays have an inverter build in. These kinds of cdi's gets their power directly from the battery.
I put a CDI system in a Ford 4 cylinder Cortina many years ago and straight away noticed more power and better idling , except one night i noticed that the engine was idling roughly when I opened the hood it looked like a Xmas tree, sparks leaking from all over the spark plug leads .The higher induced voltages must of been to much for the leads , the simple solution then was to buy HV insulating sleeve and install the leads inside.
Excellent description. Just what I was looking for. It's difficult for me to comprehend how my new CDI distributor on my 1974 Ford 302 V-8 manages to "trigger" with the components I see withing the distributor cap. Not that it makes an difference, but mine is a marine application. Thank you very much for the description.
This circuit is used in motor bikes. If you want to kill the engine, u use stop switch which will short the exciter coil to ground providing no current to spark plug and ur engine comes to stop.
Excellent! I will use your video for reference when I get to this subject on motorcycle electrical systems. This is the quality of tutorial I remember from Airframe and Powerplant mechanics school years ago. (Mostly great quality WWII training films). JB
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Highly invaluable video, I saved a lot of time and money making my own CDI circuit from basically exactly this schematic for a 125cc dirt bike. 100ohm resistor, 1n4007 diodes, 1uf 250v cap and a BT169D thyristor.
Hi good work frank this project, I need to make this CDI of my dirt bike he is a suzuki rm 125 92 you know its work on my motorcycle? send me a e-mail please i realy need this project help me please, sende from: ph_monteiro2005@hotmail.com
HI All American Five today I opened an original dirt bike CDI, I can see to have a 250v orange capacitor, I am from Brazil, but I did not think to buy this cdi here and when I thought it was very expensive 450 500 $ How Do I understand enough of electronics to make my own cdi
Interesting. I was trying to figure out an Amazon review for a small engine accessory coil to provide 12 volts for gas engine bicycle lighting. This reviewer said that just adding the aftermarket coil (approx 180 degrees from the ignition charge coil) kept his engine from running more than 3,000 rpm. We used to do this exact trick with old Ducati and other euro "scrambler" dirt bikes that only had one magneto coil so we could get some lighting, and it was never a problem. Of course, those were the days of separate spark coils with contact breaker points (and incandescent lights that didn't care about the non-rectified AC pulse from the lighting coil), but still, I'm having a hard time understanding how adding another coil would possibly have any affect on the CDI system. The aftermarket coil is grounded to the engine and has one power lead coming from the other end of the coil, so both the ignition coil and the aftermarket lighting coil share the engine block as a ground - but that shouldn't be an issue... should it? Strange, eh?
The best electronic teacher I never had in my life ! Thank you so much to speak so slowly for foreigners ( like me). Everything is so clear. Thierry ( from France)
I have been trying to learn and diagnose a small engine with no spark. these type videos are great ! Im almost amazed at the effort people put into these videos and the value that we all can get out of them. Im no engine or electronics expert but i know enough to fix some things and other times royally ruin things. I might be totally wrong but it doesn't make sense to me that the ignition's primary coil is grounded directly. I figured it would get the solid ground thru the gate(SCR/transistor or whatever it is)
Hello sir. Thank you for helping us along understand some of the mysteries of modern electrical automotive systems. I have a question if you don't mind. In a typical application of the CDI, how many "charge cycles' would you say is necessary to create enough charge in the capacitor? I ask because I really wonder how charging the capacitor is accomplished on say a single cylinder 2 stroke motorcycle engine. If a 2 stroke fires every single revolution of the crank shaft, and the CDI magnet system is tied to its rotation, then you pretty much only have 1 charge cycle (edit: 2 charge cycles) available for charging the capacitor. That is unless you use a gear system to speed up the shaft for the magnet system.
Well, the magneto rotor has multiple poles so there are many "charge cycles" per revolution. Also the pulse coil is usually on the flywheel so even 4 stroke bikes have 1 spark per revolution, a "wasted spark"
GREAT description of how a CDI works, easy to understand. I need to build a CDI for a motorcycle engine that uses two trigger coils. One at 10 BDTC and another at 35 BTDC. I assume I'd duplicate the SCR to the trigger circuit. But how would it "switch" to the 35 BTDC trigger as the engine speeds up? I need the advance to occur before 2,500 rpm.
Hi my friend, good video, I like to know if all kinds of pick up coils generate low voltage to excite the CDI? My engine is an RM 125 and 92, but it did not generate something voltage i think have a problem from my pick up coil, what do you think ?
Transformer Basic Parts & Function ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-q3YhbugYjJY.html Transformers, a few basics ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-UvHCQswnjEg.html Transformers, basic phasing ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-BRBqUQPLk-M.html
If there's current flowing through the primary coil even with the trigger off, what's stopping the voltage from being stepped up to the secondary coil and firing?
When the capacitor is charged, think of it like a battery. Positive on the left and negative on the right. When the SCR fires think of it like a wire. Now you have Positive and Negative voltage across the primary of the ignition coil.
Electrons flow from negative to positive. When the capacitor is charged and the SCR fires the electrons flow from the right side of the capacitor through the primary of the ignition coil up through the SCR to the positive side of the capacitor completing the closed circuit.
So electons flowing down from the right side of the capacitor don't see the ground as attractive and are eager (so to speak) to flow up to the left side of the capacitor.
Thanks Rick for uploading this video,, little bit of insight for others. Pulse coil is the one which would trigger when piston comes to top dead center in motor bikes. IN four stroke engine, u have intake(getting GA), compression(compress the GAS), spark(spark the compressed gas) and exhaust as four events, u want to spark the engine at the top of compression stroke, pulse coil will provide pulse exactly at that stage.. In Cars Transistor is used to pulse the coil ground and power is steady
CDI isn't the "black box" you thought it was. An SCR, v. a transistor, is used to ensure a more complete discharge of the capacitor to induce more voltage in the secondary coil. An SCR conducts until a reverse voltage is applied to its gate or, in this case, the capacitor fully discharges.
If the trigger is given to the SCR not only while starting the bike, does it mean that CDI is required even for running the bike smoothly? My motorcycle under cold conditions burps out for about 5-10 minutes past starting and switches off while the throttle is not revved (I set the idling to its best form but this still happens). Because of this fuel efficiency has severely been plummeted, do you think there might be a problem in the CDI. (I kind of related this to the CDI because my bike tremendously burps out through the silencer whenever i start).
hello, i have an 50CC 4stroke motor and its blocked at 45km/h :( common problem right? now i thought i should make my own CDI since i cant buy one thats unblocked should this work? what u made here? and will it then run unblocked? i hope u can clear my mind :D kind regards, me
If I'm understanding this correctly, the maximum voltage that the capacitor can charge to is equal to the maximum voltage produced by the stator coil (excitor). Is this correct? From what other folks have said, on scooters at least, the stator coils produce around 60 - 100 volts.
Nice video. As is can see it, the function of the ignition pulser is triggering the gate of the SCR. This means that current in the wires of the pulser is actually under 1A. Am I right???
Jovann Pérez Yes, the gate current would be very small.
9 лет назад
AllAmericanFiveRadio I checked the flowing current thru the wires of the ignition pulser. As u said and I expected it was a little one. 1.5A are required to strart the engine of and 200cc motorcycle. Thanks for your excellent video.
Does this mean that the CDI boxes are standardized or is each one unique to the motor they fire? I'm having trouble finding a replacement for my CDI and was wondering if it could be remade easily.
hello I want to upgrade my ignition system I have a opel ascona c it has a singel coil h.e.i with a inductive triger distributor and 4pin ignition module evry thing I did understand. I have all necesary components to build a cdi ignition ore have 2 ignition systems in the same time what I dont understand is the exciter coil with magnets what device can do the same effect? that pulsing movement to the capacitor? alternator?small generator?inverter? selenoid what culd I use to get the charge on the capacitor?where are those sensors located?how much I did understand one is above the engine one at the botom right? if so does those sensors ore triger can they by brought like aftermarket parts and instal them on older engine's? what effects you wuld get if you add hv diodes ore hv capacitors directly to a non cdi ignition system??? how does it effect engine perfomance and economy? what hapen if you add hv capacitors ore high amp capacitors to car baterrys what effect does it have on other car gear?how much I know is that fuse's restrict amps but not voltage will the car still run fine ore it will speed up the electric motors locaded in the car giving them more power?will the ignition coil propertis by affected?
I sorry but I can not help you. A RU-vidr sent me this circuit and asked me if I could explain how it functions. With a few question back and forth I got enough information to make this video.
Could you run it from 6 or 12v dc battery? Or is AC (no current cycle through diode) necessary to enable the SCR to shut off after it has been triggered?
Hi again. I have a link to a cdi I think I can use. I was going to mirror the circuit to get two trigger inputs and two outputs. The original mercury circuit does exactly that but uses two unidentifiable transistors to dump the charge instead of an scr. Do you think it can be done with this circuit? Many thanks in advance for looking
Wouldn't the polarity be the opposite of what is shown? I would think the negative part of the cycle would be feeding electrons to the capacitor since electrons have a negative charge.
A rectifier (diode) only allows current to flow in one direction. To utilize the other half of the AC cycle, a diode bridge would be used (four diodes), and the circuit would also need to be reconfigured. Google “diode bridge”.
Thanks for the demo was wondering how I could reverse engineer this and I think I can now. I have a bank of coils discharging into a network of caps. I then want to discharge these caps while effectively swapping the coils onto another bank of caps so I can charge these while discharging the other bank then swapping back to the other bank and then the whole sequence repeats. Just one query shouldnt the primary coils emf collapse as the cap discharges then induce into the secondary coil and across the spark gap?
One should have explained how the SCR switches off after it discharges! the capacitor so that the capacitor is able to charge once again to repeat the cycle.
Silicon Control Rectifier SCR Basic DC Circuit ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ImyTwZGZ-Ls.html Silicon Control Rectifier SCR Basic AC Circuit ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-45H4J_S52Y4.html
On the old 2 stroke motorcycles I'm playing with, there seems to be no mechanical advance. Do some electronic ignition circuits have a circuit that effects ignition advance? Or on these motors is spark advance a fixed value.
the best explanation and workind of this circuit i have seen. my question on this is a ac cdi what is difference between dc/ac operation other tha alternating and direct?
Silicon Control Rectifier SCR Basic AC Circuit ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-45H4J_S52Y4.html Silicon Control Rectifier SCR Basic DC Circuit ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ImyTwZGZ-Ls.html
Hi! I really appreciate your video and is very interesting and useful. I have a question: What software did you use to make this kind of animation? Thanks and keep going to make more videos.
Thank you, and your welcome. I use: CorelDRAW Essentials 2020, Photoshop Elements 2018 Editor, Adobe Premiere Elements 2018, in this order. Hope this helps.
...so in a CDI ignition, the spark plug fires when the SCR switches the primary circuit "ON".? I have seen other systems where the firing circuit arrangement is such that the spark plug fires on the RELEASE of the primary voltage. Does this one fire the plug on the RISE of the PRIMARY coil (thus the RISE of the secondary)? THIS MAKES SENSE--I even tried it and it works fine!
....it's interesting. Top explanation was given in our homegrown Australia Electronics magazine 51 years ago and revisited in 1975. ..In conventional Kettering ignition system it is the sudden collapse of the built up magnetic field in the coil which built up in say period of ½ a millisecond collapsing in say ½ a microsecond that generates around 400 volts in primary of ignition coil ( (this phenomena for voltage boost isn't so familiar to many )) which then is instantly stepped up to around say 30 kilovolts by familiar transformer action of coil..With cdi however the 400 volts already is supplied available thus merely needs to be dumped by capacitor action across the primary instantaneously, and capacitors are very good for instantaneous dumping , a 1uf capacitor rated for at least 400 volts is plenty for high energy sparks up into very high revolutions for multi cylinder engines...Also cos it's the effect of forced voltage feed instead of magnetic collapse it turns out that the polarity of the spark is changed. The ideal is for the centre electrode to be negative cos it's hotter,, along lines of vacuum tubes,, but not a big deal . .gotta mention too maybe that in Kettering ignition that it's initially 12 volts across the primary that builds up to 400 upon magnetic collapse when ignition points break contact.
Good video this is a cdi is powered by alternating current is clear but I would like to agás an equal with a TCI that is fed by the battery to direct current porfa I thank you
Capacitors, DC and AC Current ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-NInt1Ss3vQ4.html AC Alternating Current, for the Beginner ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-xVbqMFkyuXI.html Transformer Basic Parts & Function ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-q3YhbugYjJY.html
Hi Rick, Thank you for going to all the trouble to make this up and help a lot of people. One thought - you keep saying the capacitor is "storing voltage", or "a little more voltage is put into the capacitor" - I think what we mean is storing amperage, or storing current? I don't think capacitors store voltage, correct? Please correct me if I'm wrong. Thanks!
When the SCR fires it is like a wire, and that supplies the ground. Silicon Control Rectifier SCR Basic AC Circuit ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-45H4J_S52Y4.html
Hello, what a great explanation of the cdi using that drawing. I do not have a wiring diagram of my CDI. What brought me here was an issue with my ATV whereby I have capacitor voltage (300v) at the primary of my coil all the time. I have a dc system and I'm unsure if the CDI is bad because the SCR is and being triggered all the time, or there is some other issue. Its a strange issue and I'm not alone as many have mentioned this issue but unfortunately I have yet to find an answer. Any light that you could shine would be extremely helpful for one wandering around in the dark.
If the SCR is good, it needs to be turned ON and then turned OFF. To troubleshot a circuit you need to know how each component functions. I did a viedo on a SCR, it may help you understand your circuit. Silicon Control Rectifier SCR Basic AC Circuit ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-45H4J_S52Y4.html
@@AllAmericanFiveRadio Thank you so much for this. I will check it out. It would seem my SCR is always triggered on which surprises me because I thought it would fail open.
actually, now that I look at this schematic further, I getting even more confused. Again the schematic shown here may be perfectly accurate, but along with my other post....... I assume that the capacitor is a non-polarized type, and maybe only it's positive leg should be tapped into the line going to the primary coil. and the other leg grounded. and the positive (+) and (-) signs are throwing me for a loop too. + next to ground....
Ignore all of the polarity signs. Then draw wires to connect all those ground-symbols together. Then erase the ground-symbols. This will make the circuit easier to visualize. The capacitor is a big, high-voltage, non-polarized device. It is in series with the SCR, which is just a switch operated by the trigger switch, and also in series with the DC source formed by the magneto plus the left-hand diode, and the primary coil. When the trigger switch renders the SCR non-conductive, the magnetic field in both primary and secondary coils will collapse. The collapse of the secondary's field produces the necessary high voltage across the plug electrodes.
Hi, is the signal wire to the coil AC or DC ? I have 2 motorbikes and the coil on the one motorbike has a positive and a negative terminal (signal wire to coil connected to negative side) and on my other motorbike it only has the signal wire going to the coil it so I presume this is the positive side and the body of the coil must be the negative?
yes that is correct some motorcycles especially with older bikes the coil only has one wire because it grounds through where it bolts to the frame but in my experience the bikes that have one wire coils and ground through their mounting surface are pre-cdi ignition bikes.....
Yes without the diode operating the ignition stop switch would kill the engine and stop the ignition from firing. Without the diode there would be twice as much current through the exciter coil which also means twice as much heat. The designer of the circuit has determine that there would be no damage to the exciter coil by adding a diode, and ignition stop switch still stops the ignition from firing.
Hay bud, I have a system that's putting out 18v from exciter coil and only 6.5v from cdi box to the ignition coil. Is this normal voltage drop, or is the cdi bad? I have spark, but weak. I can hold plug in hand and just feel voltage. Any advice would be great, thank you so much, Mike.
Hi Rick. I had to figure out why you didn't just have a battery connected to ground and the anode of D1. It took me a few seconds then it hit me. The cap would never discharge. Nice demonstration! Tom PS I see SpeakerFreak95 is back! Does he still live close to you? I hope he is still using that AM transmitter that you gave to him.
Hi, I have seen someone put capacitor on coil side to make plasma effect on spark plug. Connected to earth and HT cable side. Do you have an explanation of this purpose.
A very very good video! I actually learned a great deal. However I would like to respectfully challenge the circuit slightly, and I emphasize the word challenge because I am also unsure I am just throwing something out there. I believe one of the grounds should be in between the right side of the capacitor and above the primary side of the ignition coil. Instead of its current location in between the primary side of the ignition coil and after side SCR. But again, I am not sure, I just think it would be more right?! Please give me your thought. And thank you again, great simplified video, which gets right down to the point
The thing to do is to look at what part is doing on the engine. The manufacturer can call the parts anything they want, usually because of copyright/patent infringements.
Great informative video. I have a CDI on an older motorcycle. It only makes a spark once when I push the stop button and the rest of the time nothing. I'm thinking either the SCR is bad or the trigger coil is bad and the stop button is actually discharging the capacitor.
Hi Great skematic of a CDI ignition. I'm trying to adapt a CDI box to my positive ground 1967 MGBGT using a commercially available CDI* unit with the following wiring hookups. Black/Red= stator coil Black/White= goes to kill sw. Orange = to ignition coil Black= ground White/red= Trigger Is it possible to just use 12V Dc instead of a stator coil, and a regular set of ignition points as trigger? Any feedback is welcome. Thx Rick (Lauren's Dad) * CDI 1538 for a Yamaha 1991-2002 YFS200 YFS 200 Blaster
AllAmericanFiveRadio yea but all you need is 12v in a dc cdi set up and that sends the around 400v needed to the ignition coil the coil makes 20,000 u need to jump the gap on the plug so to the answer to the question it is possible to use battery volts 12v dc to power an ingition system instead of a stator coil you just need another way to get the primary volts right.
I would contact the manufacturer of the motorcycle engine. They would have the best knowledge of what ignition system will work for their engine. Also I would study other manufactured CDI circuits. The reason for this is, if you try and reinvent the wheel you'll find out that somebody else has already done that. So looking at other successfully engineered circuits can save you a great deal of time.
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yes modern car have Cam sensor(provides which cylinder is top), and crank sensor(provides whether cylinder is approaching top dead or not) is fed to ECM/PCM, then PCM will send pulse signal to ICM(igniter) which will momentarily supply ground(using transistor switch on / off) to the ground side of the coil, note positive is 12 volt connected all the time, this makes a spark..
I normally watch your radio videos. My 1984 Honda "Big Red" stopped running. What a pleasant surprise to find YOUR video covering this! Great job as always. The Big Red is running now, by the way. Thanks again my friend!
No pulse coil in car's. I would guess this is an ignition system for a lawnmower but this is just a guess. Modern automotive (and motorcycle) ignition systems are slightly more complex and use a crank sensor and a camshaft sensor (faster start times) and do not generate their own power from a magneto as this demo shows. All the other concepts are the same. Very nice demo Rick.
Rick, I am not clear on one area, when capacitor is charging one side will be negatively charged and other side will be positive.. please advise which side is what and how this is animated during discharge, Thanks so much for uploading this video.. I gave little insight in my othe note..
@@AllAmericanFiveRadio ok , I'm a career automotive tech who works for a fleet shop . We have a bunch of ATVs and UTVs that I recently have been assigned to work on . On the automotive side I use an Oscilloscope to help diagnose ignition system issues as well as many other issues . I hooked my scope up to a Yamaha rhino with the 660cc in it and the pattern I got looked nothing like an automotive ignition pattern .. So I been searching for any resources to help confirm my theory of how this system fires and how to interpret the scope pattern for troubleshooting purposes .
In addition to my other note, cars don't use CDI(capacitor discharge unit), rather it uses Transistor switching the ground side, with positive connected to positive side all the time.. hope my 2 notes would have made sense.. CDI is used in Motor bikes and transistor switching is used in Cars.
I have one doubt from your schematic, weather battery is needed absolutely .Or the magneto is enough to produce power to charge the capacitor and work to the dynamics of the ignition system pl.
+tjmars37 Yes it would still work. When the crank turns in one direction + - + - + - voltage is made, when the crank turns in the other direction - + - + - + voltage is made. This circuit is using only half, the + half and it is created in both directions.
Thank you. You would need a high voltage test oscilloscope test probe. The probe would have to handle several thousand volts so that you do not damage the oscilloscope. GOOGLE “oscilloscope spark plug probe” and “Images for oscilloscope spark plug probe”.
@@AllAmericanFiveRadio ok. I was actually trying to probe the primary side. My scope can handle 1000 volts. I know the primary puts out about 250 volts when running. Thanks.
Are there alternatives are there to Capacitor Discharge Ignition? I am specifically referring to a magneto type electronic Ignition system. If there are no points and condenser, is it automatically assumed it is a CDI type ignition system? A reference to some schematic would be really appreciated. Good video BTW.
