Futterama

Hi,

I have now received both the LT3750 and the DA2034 but I don't know when I will get the time to work with it. The coil looks nice and small and the LT3750 is a 10-Lead Plastic MSOP and that is smaller than the SOIC I'm used to work with, so there is a challenge for me just to solder the LT3750

Uwe, please notice the Recommended Board Layout on page 11 in the LT3750 datasheet before testing


/Martin

aerodactyl

Hi Martin,

last Friday I received the coils, but I'm still waiting for the LT units.

The coils I ordered were the small and the medium version 3A and 6A (each 3 parts ) They really looks nice and small. Let's see how they will work.
Yes, I'm aware of the layout. Next week I propably will find time to make a test layout for my system.
I will keep you informed.

Best regards from a snowy Germany

Uwe

captinjohn

BigBoat, I have a question. I am hooking up different sensor wires that use 3 wires to pick-up. I was wondering what happens when the + and minus leads are unsoldered and switched, leaving the center where it is. Will the ignition still work...by fliping the magnet in hub thus changing polarity (North & South poles). Or will the system not work at all? Thanks Capt,n

Bigboat

The problem can be a variable ignitiontime.
The ignitiontime must be exact and not *somewhere*.
By using two magnets, one for the ignition and one to filpback, maybe it will work.
BUT, the charge-time will be shorter, your missing the piece between the two magnets, and also the max-rpm will be lower.

captinjohn

The system I was working on did not fire and I found a unsoldered pin in a connector lead to pickup sensor. Would this ruin the picup sensor or other parts in the CD unit itself? Thanks Capt,n

Bigboat

NO.
If the lead was the +, and contact the pulslead the cdi fired, if the + contact the -, the cdi didn't do anything at all.

captinjohn

Big boat...what are the normal wire colors that go to sensor? You know ...like 3 wires...3 connections. Is red + ? Black - ? and middle wire??? In other words what color goes where in a normal setup? Thanks again Capt,n

Bigboat

Red = +, black = - and every other color can be te puls.

captinjohn

I guess I got to read more on your website and maybe simular ones too. Best Regards Capt,n

Happymcc

My Feedback: (1)

Hi to all
Is anyone selling the EEprom's already programed ?

Phatburner

Hello everyone;
I found this forum while looking for information on home made CDI. I want to thank those who have done so much work and for sharing. I would like to join in the development work with the LT3750 and am ordering it along with the DCT20EFD transformer made by TDK which is available from the local supply. I am surprised you guys can run a CDI from batteries as I did the scratch pad calculation to reveal that with 80mJ spark at 12000 rpm that means 16 watts if the efficiency is 100% so it must require around 20 watts from the battery. This is no small power and I am wondering if your engines have a generator??

Joe

Bigboat

No generator, only batteries and the CDI can run for about 6 hours on a 6V 2000mA NiMh.

Bigboat

A preprogrammed PIC is not possible becourse you need the curve of your engine programmed.
Not all engine start at 30 degrees befor TDC.
You have to make the curve by yourself and program the PIC with it.

Happymcc

My Feedback: (1)

Thanks Bigboat
Thats to bad though
Would'nt RC engines be pretty much the same across the board ?

STMCU

Dear Rob,

I am the new comer but i gone though the topic. I have some questions and would like you to answer.
1. Is your CDI be able to work on 4 strokes engine ?
2. I have to use coil sensor ( instead for hall sensor), is it possible ? If not, how i adjust the schematic ?

I intend to build a CDI for motorbike engine ( 100 cc). Now i will start and hope to get your help.

Thanks in advance.

Tung.

jpanhalt

Happymcc,

If you are unable or unsure of how to program the PIC chip, there is lots of help available. Many electronics hobbyists will be able to do it for you. Almost certainly, high schools and local colleges also have the ability. It should cost nothing and takes almost no time to do, once you have the code in electronic format.

Check around. If you strike out, I would be happy to do it for you using the "standard" code.

John

Bigboat

The CDI can be used on any engine even on a 4 cilinder.....with a little help of a electronic/mechanic switch.
It doesn't matter if you generate a spark in the exhaustrotation, the petrol is all ready be burned.
You can also use a counter IC (CD4017) or flipflop who release the spark every second count.

I don't understand a coilsensor ?
A CDI need a exact ignitionpoint to spark, it's much faster then a normal pointswitch.
You can also use a opto-sensor with a black/white disk or a hole into a white the disk.
Something like this, only with one white line

Happymcc

My Feedback: (1)

jpanhalt

And all others that replied . Thank you for your time and info .
I have been using C&H ignitions for years and have gotten good service from them .
Right now I am working on converting a few glow engines to gasolline and strait methanol .
I have also seen a very simple internal oiling systme that I intend to try .
In researching engine conversions I ran across this thread on ignitions and maybe after
I get done experimenting on several 4 stroke conversions I think I will make one of these
ignitions .
Again thank you all and I will be back for help I am sure .

STMCU

Dear Rob,

I meant coilsensor is magnetic or inductive sensor. Hall sensor produces square signal, using 3 wire (+/-/signal) and magnetic sensor produces a.c signal. I don't know if your CDI can be used with magnetic sensor ?

Regards,
Tung.

Kymmy

Problem there is where to fire the coil on the resulting curve, also then temp variation would mean that it would fire sooner or later dependant on how hot/cold the circuit got... Best to stick with a latched Hall sensor

Kymmy

Futterama

I have just downloaded a simulation program for the Linear LT3750 and I set the cap to 470nF and the result is charge time 0.6ms to 150V and 2.9ms to 400V, so it looks promising.

Bigboat

20ms = 50 Hz = 3000 RPM
2,9ms = ~350Hz = 21,000 RPM

The Voltage is also OK, it have to be between 400 and 600 Volt for a good spark.

STMCU

Dear Rob,

I expecting your help to build the ignition advance timing curve for 4 strokes engine 100cc. Position of pickup sensor is 36o. Engine spark at 15o at low RPM and 27o at max RPM.
max RPM with full load is arround 8000 RPM and 12000RPM at no load.
I looked through the excel file which you showed to make timing curve but i don't know why you set POP (point of pickup) BTDC is 40 ?

Can you help.

Tung.

Futterama

Hi again,

I wrote Linear and Coilcraft, and they suggested me to use the new Linear Technology LT3751 with a CoilCraft GA-3460-BL. This will charge a 200µF capacitor to 500V in 200ms with an input voltage of 12V. So I guess it could charge the 470nF in about 0.5ms with the input voltage at 12V. The voltage range goes all the way down to 4.75V so it will also run on 6V, but the charge time will increase, but I guess it will still be below 2ms.

My goal is a charge time around 2ms so I can use the CDI on a tuned Zenoah G260RC (on FG RC cars) - these can run above 20.000rpm so if the CDI can handle 30.000rpm (2ms), it will be fine.

Also, I think I will add a separate battery for the CDI, I don't think it will be a good idea to use the receiver battery because of the power consumption and electric noise.
I have another project going on, which will require 3 or 4 cells LiPo to be mounted on the FG car, so I will have 11.1-14.8V available for the CDI also.

Futterama

Bigboat, at which RPM can your CDI run for so long on that battery?