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Autor Thema: Transistor-Zündanlage, Do-it-yourself-Bauanleitung  (Gelesen 4707 mal)

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Transistor-Zündanlage, Do-it-yourself-Bauanleitung
« am: 01 Mai 2011, 14:52:55 »

TIM 1 Transistor ignition module

Why? No reason really the points condenser set up in these singles are perfectly adequate. Especially with the single cylinder engine there is no lack of time (dwell) keeping the points closed for full coil saturation. So why? Mostly to satisfy a curiosity and rekindle a very basic interest I had with electronics years ago.

I'm no electronics guru, it wouldn't be hard to know more about electronics than I do. So your more than welcome to contact me and make comments or suggest any mods that could be made.

The module does however have a few advantages.

* There is no need for the condenser.

* Since the points are only switching milliamps there is no danger of the points becoming pitted and burnt. Theoretically they should last almost forever.

* The switching is done almost instantaneously through the transistor, inducing a high current to flow through the secondary windings giving a hotter and "fatter" spark at the plug.

* Easier starting and cleaner fuel burn.

* And it can be easily reverted back to the standard setup.

Tim1 still uses the existing points setup to do the initial switching in the primary circuit, however TIM2 will incorporate a hall sensor to do the on off switching making the setup almost fully electronic! Wow.

After bench testing the circuit I built my first module. Since the condenser is no longer needed it provides for the perfect place to secure the TIM1.

Transistor ignition module testing and the finished unit mounted on the points plate

I sent my first TIM1 to a friend in France whom also has an R25/3 and asked him to test it for me. My greatest concern being heat. Electronics don't like excessive heat and under the front cover of the generator things can get pretty toasty!

Oliviers first report,

Hi ben,

I've starded to test your system last week-end on my byke lately on sunday evening! So the trials were in my parent's garage, it was so rainy outside that I wasn't able to drive outside. I've wired the electronic ignition instead of the condenser without fixing it on the contacts block, because of a matter of time...

Before that, i've started the engine with the original ignition to be sure that nothing else could matter in the change. Everything was working perfectly, so I've wired your device.... One shot on the kick to start the engine and....It works!!! So I decided to let it work some seconds at a low speed. Then I accelerated the engine and 15 seconds later everything stopped... :-(

I thought at first the electronics could have burn but nothing was hot. So I've checked the cables and I've wired it again.. The problem was with the ground- I choose a point with bad conduction-. So I started again the engine and it was OK :-). The other problem I had then was that my engine was too hot and started to be difficult to start. I hope I will have time this week end to fix it completely and try it on the road. I'll take also pictures of it for you. The difference with your ignition is that my coil is not the original one, it's placed under the tank and not near the contacts under the cover box. A small one is very expensive and I've heard that it's sensitive with heat in the front box on the engine.

Oliviers second report

"I had some rides around my parents house, and it was really good! the engine seems to devellop more power, and NOW the starts are really easy ( easyer than before, because it was starting really well before but today it's more powerfull)"

"I had a ride with my bike yesterday, it works well, and I say again : the engine seems to developp more power ...

"I'm very glad that in the end the ignition was working good, and it's interesting to see that the engine developed more power, and you asked maybe you are imagining it :-)))".

This feeling comes from the acceleration which is better, torque also at low motor rpm; perhaps the maximum power is not increased, I should test it with the maxi speed to be sure...that I 'm not imagining it ;-)."

Pictures of the TIM installed on Oliviers bike

You too can build a TIM1

The five components needed

Although I'm suggesting that it be for the r25/3 it should fit all models from the R24 through to the R26. These models all used basically the same generator housing and points plate. The differences in power generation between models are of no concern since the ignition consumes so little energy.

This circuit uses the original points to switch the transistor, which in turn switches the low voltage windings of the ignition coil.

I'm using a 10Ohm resistor (R2) between the points and base of the transistor to keep the amperage in check though still provide enough so the transistor is saturated and will switch full amperage through the coil. By actual measurement the points are only passing approximately 70mA.

The PNP transistor (Q1) used is a TIP2925 power transistor, which is capable of switching up to 15 Amps more than enough for the ignition system. In reality just about any PNP transistor can be used as long as it has the required power rating.

(D1) is a backwave diode to protect the transistor from the high negative voltage generated by the collapsing magnetic field in the coil. (D2) is a LED, which is used for timing purposes. When the points are open the LED is on, when the points are closed the LED is off. It's also there to indicate that there is some life in the system. (R1) is a 470Ohm resistor to keep the LED amperage in check.

At this point I must emphasize that at no time should the ignition be left on with the points in the closed position for long periods of time. The transistor will be passing full current continuously and it may get "fried", not to mention that the coil will overheat.

Building the TIM1

There are many ways of making the Printed Circuit Board (PCB) though I used a very rough and ready method. If you really want a professional looking board then go here http://www.electricstuff.co.uk/pcbs.html This site has lots of good information for making PCBs. My method uses the minimum of equipment.

You will need

1 Single sided copper clad PCB

2 Permanent marker or etch pen for drawing onto the board. Through the suggestion off another site I found that the Staedtler Lumocolor 318 Red permanent was the best.

3 Ferric Chloride for etching the copper

4 A selection of very fine drills 0.4-1.2 mm

5 Acetone for removing the permanent marker after etching and drilling

6 Scotch brite pad for cleaning the PCB before soldering the components to it.

7 Soldering iron with a fine tip and solder

The first thing is to cut the PCB into shape; small 2.5 X 5.0cm rectangles are the correct dimension. You will need a very fine toothed hacksaw or jigsaw. Cut 3 or 4 pieces as you may make mistakes while etching, drilling soldering etc.

Plan on the PCB where you want to place the components. For this I used a piece of cardboard and stuck the component pins through the card, you can then mark onto the PCB where each of the components will be placed. The component pads can be drawn with a stencil and the tracks in between can be drawn free hand. Once the pads are drawn it's basically a matter of joining the dots with the marker. Make sure that the pads are large enough to get a good connection between the solder and components. Especially with the transistor as the pins are rather large. The other components have much finer pins so the pads can be smaller in diameter.

The tracks from the transistor to the base and coil output should be at least 3.5mm in width, enough to carry the current. Between the other components such as the LED the tracks can be much thinner as the current is much less.

Allow the freshly marked PCB to stand for a while allowing the solvents from the marker ink to evaporate fully.


Getting a good clean etch is the most difficult part. What we are doing is dissolving or etching away the copper that is not protected by the marker ink. Only a very small bath is required, I used a simple water glass. Ferric Chloride is extremely corrosive so you don't want to splash the stuff around, especially onto your hands and into your eyes. Use protective gloves and eyewear.

250gr of the Ferric Chloride pellets will make up 500ml of solutuion.

The etch process is also improved if the bath is kept at a constant luke warm temperature, approximately 40C. You can do as I did. Start with warm water when first dissolving the Ferric chloride crystals and then place the glass into a bowl of water on the electric stove (better to do this when wifey is not around)

The bath can be used several times so it's a good idea to mark and etch a few boards just to get the messy part of the project out of the way.

The etching requires constant agitation and it's best to have the copper side of the PCB facing down to allow the free copper to sink to the bottom. You can either stir the bath continuously by hand or do what I did and sacrifice the fish tank air pump and constantly have a jet of air blowing into the bath to keep the solution moving. This also gives a much faster etch with cleaner track lines. The PCB can be removed periodically from the bath to observe the progression of the etch. It is quite obvious when the etching is complete.

Remove the PCB from the bath and rinse it under cold running water. At this point we have the component pads and tracks remaining on the board. I like to leave the marker ink covering the tracks until after the drilling.


It's really handy if you have a dremell and a small enough chuck to hold the drill bits. There are purpose built drilling machines and stands for drilling PCBs, however if your very careful you can drill the component holes by keeping a steady hand. Try to keep the drill bit as perpendicular to the board as possible, and drill through the board into a soft piece of wood. It also helps if you can mark the center of each pad to be drilled with a very fine center punch and a light tap with a very small hammer.

After the drilling is complete you can then use the acetone to remove the marker ink from the PCB and then rinse again under cold running water. Your left with the shiny copper pads and tracks ready for the components to be soldered to.


Before placing and soldering the components it's a good idea to give the copper tracks a light rub with the scotch brite pad, especially if you have left the board standing for a few days. This helps to remove any oxidation that may have developed which prevents a good solder joint.

The components can now be placed on the PCB. The pins pushed through the drilled holes. Do not trim the pins until you have soldered each component. Also do not forget to solder the connection wires, there are three wires. One goes to ground, the second going to the negative side of the coil and the third to the points.

I'm no expert on electronics soldering, suffice to say that you try not to overheat the components. These components are not particularly delicate so even the greenest novice should be able to complete the soldering.

I finished the TIM1 of by spraying an electronics lack on the back of the board. These lacks are silicone based and heat resistant, which will guard against shorts and protect the copper circuit from oxidation.

Thanks to Olivier in France for testing the TIM for me, and to Bart in the Nertherlands.


THIS SITE WAS TAKEN FROM BEN´s BMW-SITE (http://bensbmw-r25-3.freeservers.com)
« Letzte Änderung: 25 September 2014, 10:21:11 von Karl »
Vorsicht! Dieser Beitrag kann Spuren von Ironie oder Sarkasmus enthalten. Ohne Konservierungsstoffe (lt. Gesetz). Ohne Farbstoffe. Ohne geschmacksverstärkende Zusatzstoffe. Deckt 2% des Richtwertes des täglichen Benzintalkbedarfs.

BMW Einzylinder-Forum

Transistor-Zündanlage, Do-it-yourself-Bauanleitung
« am: 01 Mai 2011, 14:52:55 »


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