bluejets

See how I go and I will post back success.
Built a few engines before and although this will initially be used in a test bed single cylinder, intention is for final use in V8.
Have 4 cylinder 25cc in scale Rivierra (1930's era) but this is methanol and glow. (Hull 60% complete)

bluejets

Need assistance on capacitors quoted in diagram as C3 and C7. These are shown as being 100 nano electrolytic.

I have been around electronics for many years and have never seen an electrolytic under 470 nano and rare at that. None are listed in any suppliers here in Aus.

Can these be substituted by 100 nano MKT / 50 volt? (MKT = metalised polyester film)

or/ is there an error in the diagram and parts listing?

Bigboat

Maybe your not long enough into electronics....
http://parts.digikey.co.uk/1/1/35748...r2a0r1mda.html

bluejets

50 years apparently not long enough...... thanks for info all the same.

No digikey in Australia though..... maybe look at RS

bluejets

Found suppliers of various parts in Australia for anyone interested.
Jaycar..... (C6) 470n/400 cap (630v in this case) RG-5247

Farnell..... (C3 and C7) 0.1uF/63V electrolytic order code 9452729
Hall sensor (Allegro) A3240EUA-T order code 1141949 (used these before with other ignition systems I've built)

Oatley Electronics ..... Surplus fluro inverters for ferrite trigger transformer ($4.00) part No. CFLINV
Also small magnets 3 x 1.5 .....part No. G58 ($0.25)
(use these before also and they work ok... leave about 2-3mm gap between magnet and sensor)

All other parts from Futurlec (on-line http://www.futurlec.com.au/Components.jsp )

I have not at this stage wound the trigger coils onto the above transformer bodies. So I do not know if they will work or not however, they seem to be the right size and I will re-post the results.

bluejets

By the way, if you really want to go the Digikey way, here are the responses from the US supplier and the New Zealand supplier.
The following is for the supply of 5 only 0.1 capacitors with a cost of 15 cents each.

Thank you for the email to Digi-Key Corporation. I am sorry that shipping is so expensive.
Our only options for shipment are UPS, FedEx, DHL or sometimes we can use the Unites States Postal Express. I did check UPS Express and it shows $70.00. Fed Ex express is 75.24. I did check the Postal Express and found that to be around - $35.00 or so and they say it could take 5 to 7 days for you to receive them.
I do believe the other carriers would have them to you in a couple of days.
By the way, Digi-Key Corporation is located in the United States, in Thief River Falls, Minnesota and our only warehouse is here. If you checked our New Zealand site, the shipping is still from here.

Thank you for your email! Part number UVR2A0R1MDA-ND is a non-stocking part for us. We do not stock it but we can order it for you. The minimum orderquantity is 2800 pcs. We do stock the rohs compliant/lead free version. It is part number493-1136-ND and we have 5 pcs in stock. The unit price is $0.15, $0.75 forall 5 pcs. You will have to order through our US site as you are in Australia. You canonly order through the NZ site if you are shipping to NZ.
Sorry for the bad news.

jpanhalt

I don't understand why you need the electrolytic capacitor at that location in the circuit. Why not use a ceramic? If you need more ESR, add a resistor.

John

bluejets

Asked this question myself (go up a couple of posts) Apparently not according to bigboat.

jpanhalt

Sorry about that. I interpreted that discussion to be about availability, not necessity for using electrolytics.

C3 is used for firing the SCR. I reverse engineered two commercial CDIs (a Chinese import and an RC Ignitions from the USA). Both used mylar/polyester. On the bench, I have used ceramic as well for that function. I can't see that a high esr would be any advantage in that application.

C7 is for the oscillator. The reverse engineered units used aluminum electrolytics, but they used much higher values of 1 or 10 uF. ESR might make a difference, but I am not so sure a lower ESR would be bad. A common, small tantalum at 0.1 uF would have an ESR of about 10 ohm (not low esr version), which is comparable to the esr of the larger electrolytics. Nichicon didn't list the esr of the 0.1 uF in the datasheet I had. By comparison to others, it probably has an esr of at least 10 ohm or as high as 100 ohm. That is just a rough calculation based on the inverse relationship of esr and capacitance given the same tan delta.

John

Bigboat

If you are using a higher value to C7, the ocsilatrofrequentie will be lower.
If the ocsilatorfrequentie is lower, the load of C6 will be lower.
If C6 have a low loadfrequentie, the sparkintencie will be lower.
This CDI is made for high rpm (>25,000), the commecial CDI you can buy handles till <10,000 rpm.
You can change C3 into a 0.1 uF MKM capacitor opens theT1 gate for X-time.
But.....the time with a MKM will be shorter then when your using a aluminum electrolytic.
The spark will also be shorter, less spark, if the X-time you create is shorter.

But, it's a opensource project so you can change everything you like.
If you can make it better, be my gast [8D]

jpanhalt

Re:C3 An SCR gate will stay open until the current through the SCR drops below the holding current. Since that is not a GTO SCR, once fired, there is no control of the open time, except for that discharge period. Most datasheets for SCRs will give the firing criteria, which is generally something like a pulse with a minimum duration, voltage, and dA/dt (i.e., Vgt and Igt). The BT151 is characterized at a dI/dt of 5A/uS, which gives a turn-on time of 2 uS. I didn't study the datasheet that carefully, and there may be more data, but I did not see a minimum or maximum dI/dt for the gate. Consider a 0.1 uF capacitor with an esr of 100 ohm. The time constant for that alone is 10 uS. Using another capacitor with an esr of 10 ohm, which gives a minimum time constant of 1 uS should not affect the gate opening.

The point here is not to criticize or to redesign the circuit, but to find available components that can be substituted and will work. Even in the USA, I am not about to buy the minimum quantity of 0.1 uF aluminum electrolytic capacitors from DigiKey.

John

Bigboat

I don't think this is a point, over 100,000 people read the CDI topics and no one complains about the componets we have used.
We have try to use no exotic componets and for all componets are replacements to buy.
But again, it's a opensource project and if you can change the CDI in positive way be my gast.
If your designe will be better, I'm happy to place the designe on our website with your name on it.

bluejets

Reference (above)... Oatley Electronics ..... Surplus fluro inverters for ferrite trigger transformer ($4.00) part No. CFLINV

Disassembled one unit to see what parameters were. It has an output winding of 380 turns 33awg. I removed a second unit and left the output winding and insulation in place and re-wound primary and feedback. Seems to work ok on testboard but not sure of effect on available energy to main capacitor. Getting around 500Vdc

aerodactyl

Hi guys,

I want to continue with my project and wanted to test the version with the LT3750. I received the parts already several weeks ago but had not time to study everything. The LT3750 is so small (10 lead MSOP Pack), no way to make a layout and develop the board at home [&o][&o] Pin to pin distance is just 0.5 mm/0.0197".
Has anybody an idea how to handle this? There are adapter boards available but board + shipment will cost about 12.- EURO. [:@][:@]
The flyback transformer is no problem. Its big enough.
Thanks for your comments.
Best regards from Germany
Uwe

aerodactyl

Hi all,

I'm looking for useful spark plug cables for 1/4"32 spark plugs. The cables should be shielded and the isolator inside the metal housing should be silicon made. Any idea where to buy these cables? I found some in the US but these were not shielded and have no metal housing.

Salut
Uwe

wilkxt

Hi sorry for my english
I built my own CDI to motorbike 600cm, i use 1.5uF capacitor to strong spark, if i use 0,47uF capacitor voltage wil be higher and curent wil be less. Don't use converter when igniton coil is disconnected or add resistor obout 100kohm instead ignition coil

schemhttp://www.ust.tke.pl/wilk/przet.JPG

This is mesure for 0,75uF cap and V=12V VCC
t [ms] Vcap [V] I[A]
8 400 0,45
7 400 0,75
6 400 0,8
5 380 0,9
4 340 1,0
3 330 0,95
2 280 0,902 ms = 500Hz = 30000 rot/min
1 210 0,851ms = 1000Hz = 60000 rot/min


regard's

Bigboat

It doesn't matter if the Voltage is high and te current is low or visa versa.
P= UxI, if P=constant, U can be high and I low or if U can be low and I high.

wilkxt

Converter's curent wil be low (not capacitor) becouse less capacitor is faster charge and if capacitor achieve approximately 400V (or less if I chanage PR1, max converter's voltage) this converter go off and avarage curent wil be less.

Nosedragger

Ask for USPS Priority Mail flat rate shipping in the small flat rate box. its $12.95 USD anywhere in the world for package weight under 4 pounds.

Rallyfinnen

Hi!

I'm new to this forum, but registered because I'm interested in your DYI ignition for my 1/5 car.

I have an idea of using only the control board to delay the ignition advance using the standard coil.
I think this should be possible by using an IGBT or similar across the terminals for the stop switch to short circuit, and then release at the time of the desired spark advance. (I've built MS to control fuel and spark on 1/1 cars before using IGBT's to drive the coils)

Not sure how the hall sensor should be trigged in my imaginary setup. Either from the stock magnet or a separate magnet added to the flywheel.. How much advance is needed from the trigger to actual ignition if the maximum rpm is abt 20000rpm? (I guess there is a minimum delay in the setup?)
If this would work, the power consumption would be low enough to run the ignition control from the RX batteries, with the stock coil generating the spark energy.

Ian oddie has taken this principle a step further as it seems, since he is supplying the control circuit from the ignition coil too!
http://www.oddified.com/services.php

I have not invested in anything yet to try this idea (some time and money would go into the PIC-programmer and control board, I especially dislike making PCB's.. )

Hope you can give me your thoughts about this so I can decide if it's worth trying..

If I understood it correctly, the ignition curve is a straight line between two setpoints. Is there some way to specify this as a rough curve instead?Say a few independent poiints across the rpm-range with interpolation between the points?

Bigboat

This is the location of the new CDI http://www.rcuniverse.com/forum/m_4344316/tm.htm
This is the link to a TCI http://www.rcuniverse.com/forum/m_9198847/tm.htm

jpharris1234

Hi All!

I recently decided to build one of these units to replace the stock fixed ingition on my son's go kart.

I currently have two units running, one test setup built on a breadboard and the other as a "production unit." I have used an off the shelf toroidal

http://www.jaycar.com.au/productView...d&form=KEYWORD

for the DC-DC upconvertor to charge the capacitor. I initially had trouble with controling the voltage on the main cap.

At first, I could get only about 180 V max. I changed C7 to .2uF and R5 to 300Ohms. This made the charger go into "overdrive." At one point I had over 1000 volts on it before the BT151 gated itself! I found that I could control this by having a ~1M pot pulling down the voltage to 400V while idle (no spark). In test function 1 (300 rpm) , the voltage drops to ~370V. In test function 2 (7500 rpm), it drops to 30V.

I am using this setup:

http://www.modelbouw.gompy.net/newcdi/cdi-a.jpg

I noticed that Bigboat had similar trouble some time ago:

I have test today the CDI and find some problems.
Sometimes I missing a spark, sometimes a spark at the wrong time or to muts sparks at the same time.
It seems to me a EMC-problem in the pcb I use, the pic making (or not) his own sparks.
Also the energy for the capacitor is to small when the engine runs high rpm.
If I calculate the power I need (5 Watt), the capacitor must be ~4,7uF instead of 1uF.
Inside the cylinder the pressure is ~12bar on 4000 rpm, with this pressure there isn't a spark anymore.
Back to the drawingbord [img]{akamaiimageforum}/image/s14.gif[/img]


Does the 1N4007 need to be inverted or has this already been udated in the schematic?

Any other suggestion to keep the charge on the main cap up to working level?

R's

JP

p.s apologies in advance if I missed the answer already posted.....I did read thru all 12 pages  & didn't find it.

jpharris1234

Ishould probably mention that Iam using a primary coil (E type) from a NISSAN 4WD.

R's

JP

Bigboat

Becourse it's the wrong topic.
There are two topics, this one where we starting to build a CDI and this one http://www.rcuniverse.com/forum/m_4344316/tm.htm of the new CDI

Altium

Hi,
I cannot open your site and I cannot see the schematics of this CDI.
Pleas give us valid URL of your project.