Introduction

This is a new design for a universal gear indicator that can be fitted to any motorcycle as an aftermarket accessory. Its main advantage is that its operation depends entirely on the gear shift lever movement, instead of connecting to speedometer and tachometer sensors (found in expensive commercial devices), which are rarely available in older motorcycles. It consists of a main circuit including a 7‑segment LED indicator, two Hall sensors that are attached to the motorcycle frame, and a small magnet placed on the gear shift lever.

The main circuit is based on an AVR ATTINY25/45/85 microcontroller, which reads the signals of the two Hall sensors and the neutral switch and outputs the current gear number to a 7‑segment LED indicator, through a 4026 counter/decoder.

At maximum output power there is significant heat produced by IC1 and for that reason we mounted it directly on the ground plane to achieve maximum heat radiation.

Schematic

Source Code

The source code is written in AVR-GCC (WinAVR) and can be programmed with the default fuses using an AVR programmer (default : ATTINY25 microcontroller and USBTiny programmer). Moreover, the constant TOP_GEAR 5 should be changed to 6 for six-gear motorbikes. Source code can be downloaded on the download section below.

PCB Design

The suggested implementation for the main circuit is a small size, double-sided PCB, with SMD packages for the microcontroller and the decoder ICs. The 7-segment LED is placed in a secondary PCB, connected vertically to the main one in a modular fashion (see pictures). Two PCBs for different Kingbright LED footprints (red and blue) are also provided.

Parts List

Possible improvement

In the current design, when the neutral switch is open (there is a gear on), there appears to be a very small current (< 0.5 mA) sinking through R3, due to the voltage difference between the neutral switch connection (TO_POWER-4) and the microcontroller. If the neutral indicator is of LED type (not a resistor bulb), there is a possibility that it stays dimmed, instead of being completely off. In that case, a small switching diode (1N4148) can nicely replace R3 (on the same PCB) in order to block this small incoming current when the neutral switch is open, as shown in the figure below :

For a better insight in the above issue, the following script can be imported in Paul Falstad’s excellent circuit simulator:

http://www.falstad.com/circuit

$ 1 5.0E-6 10.20027730826997 62 5.0 50
R 192 96 192 48 0 0 40.0 5.0 0.0 0.0 0.5
R 512 96 512 48 0 0 40.0 12.0 0.0 0.0 0.5
r 192 96 192 176 0 10000.0
x 231 142 309 145 0 12 internal pullup
x 125 25 277 31 0 24 Gear Indicator
x 456 26 571 32 0 24 Motorcycle
M 192 176 96 176 0 2.0
x 65 157 118 160 0 12 AVR Input
w 192 176 192 256 0
162 512 96 512 160 1 2.1024259 1.0 0.0 0.0
r 512 160 512 256 0 470.0
d 512 320 512 400 1 0.805904783
x 413 388 499 391 0 12 protective diode
s 512 400 640 400 0 1 false
g 640 400 640 448 0
x 539 422 615 425 0 12 neutral switch
x 309 240 391 246 0 24 1N4148
x 132 377 269 380 0 12 in place of R3, and watch
d 304 256 400 256 1 0.805904783
r 304 336 400 336 0 10000.0
x 337 371 367 377 0 24 R3
S 192 320 272 320 0 1 false 0
w 192 256 192 320 0
w 304 256 272 256 0
w 272 256 272 304 0
w 304 336 272 336 0
w 400 256 400 304 0
w 400 304 448 304 0
w 400 336 400 304 0
w 448 304 512 304 0
w 512 304 512 320 0
w 512 304 512 256 0
x 131 359 276 362 0 12 flip switch to insert a diode
x 134 394 272 397 0 12 current drop to zero when
x 134 412 254 415 0 12 neutral switch is open

… or click here for direct Circuit Simulator Link
Contributed by Brett Walach

Photos

Connections

A successful circuit build will do a self-test when connected solely to 12V power (pins TO_POWER_1 and TO_POWER_2), by cycling through all digits on the 7-segment display (see video below). After the self-test, the current gear will be shown and can be changed by the shift lever movement. Note that a gear is changed when the magnet’s south pole is drawn away from the sensor (north pole will not work). Moreover, if a neutral gear is detected (from the neutral switch connected to TO_POWER_4), the display resets to zero (also acting as a self-calibrating feature if anything goes wrong). Finally, when the power is turned off, the last shown gear is stored in the MCU’s flash EEPROM and restored when the device is turned on again.

The following video shows the initialization procedure of the gear indicator :

Self_Test

Sensor Cable

The following photos show the construction of the 4-wire sensors cable that is plugged to the TO_SENSORS connector. The visible sensor pin parts should be covered with plastic lacquer for protection as well.

After putting it all together the circuit is now operative and ready to be installed on the motorcycle. A video showing a simulation of gear shifting (by hand) is available below :

Circuit_Operation

Installation Photos

Here are some photos and videos from the installation on my Suzuki Intruder VS400

Custom Housing

Installation Videos

Installation1 – Gear shifting by hand

Installation2 – Real gear shifting with engine on

Installation3 – Storing last gear in EEPROM

Thanks for reading !

Designed and built by Vassilis Papanikolaou © 2010

Multi-spark ignition is very useful especially in the case of startings at low temperature and at low rpm range. Basic idea, is to apply to spark plugs instead of only one spark, a “spark-burst” having big energy. In this case, combustion of air/fuel mixture is much better and the emissions are more reduced. In addition, through burning improvement, the consumption of fuel can be reduced.

Why synchronized multi-spark, or what means this?

Special literature abounds in multi-spark EID schematics. These have in common the fact, as the breaker-points don’t control directly EID, but an oscillator, which will generate a succession of impulses, and these impulses shall command EID. This aproach has two major deficiencies:

1. First spark doesn’t match exactly with the moment of breaking points; so, it has an aleatory delay toward this. This is equivalent to an aleatory modification of ignition advance, which will leads to non-uniform run of engine.
2. At high rpm range, the time between two impulses of multi-spark device can become comparable with the time between breaker-points impulses; this shall lead to an unstable operation of engine, with trepidations and knockings. To avoid this trouble, is necessary to switch-off the multi-spark device when rpm of engine exceeds a certain value.
   With these in mind, I imagined the device described forwards.

Few calculations elements

The crankshaft velocity of an internal combustion engine is given by following formula:

where :

n = revolution speed of engine crankshaft (rpm)
M = strokes number (2 or 4)
N = number of sparks per second (sparks frequency, in Hz)
B = number of ignition coils
C = cylinder number

For usual four stroke engines, with 4 cylinders and a single ignition coil, the formula becomes :

From where :

In fig.1 is shown an EID equipped with synchronized multi-spark module.

Shaping block has the role to provide fixed length impulses (2 mS) at each breaker-points opening. In this way are eliminated the false impulses which appear due contacts vibrations.
As shown in drawing, shaped impulse triggers directly the EID and act as START impulse for multi-spark module. If rpm of engine is under speed limit, the module will generate a series of supplementary impulses that, through an OR gate, will generate supplementary sparks by EID. When speed limit is reached (for example, 2000 rpm), supplementary impulses stops at module output, thus no supplementary sparks will be generated.

Functional description

The module uses for control the shaped impulses from breaker points. The time between two consecutively impulses depends on rpm engine and has the values shown in upper table.

From whole T interval, only in the first half of this will be generated supplementary sparks, after the main spark produced by the breaker points. This is very important, because generating sparks outside of half of the interval, the spinning distributor could apply these sparks to next cylinder, and this could be very harmful for mechanical parts of engine.

At breaker-points opening, the shaping circuit (not shown in drawing) produces a square impulse having 2 mS. This, named BP, is applied to EID by an OR gate and generate the main spark.

In fig. 3 is shown the block-diagram of the multi-spark module.

In multi-spark module, during 2 mS interval, a sequence timer (a counter with decoded outputs) accomplishes the initialization of circuits (full operations will be detailed later). When impulse BP disappears, the gate P2 is opened and the counter N1 receives impulses with 1 mS period, from clock generator. This 8 bits counter measures, in fact, the duration between two breaker-points impulses. It can count maximum 255 impulses, each having 1 mS (see the table, this correspond to 120 rpm, far below the free running speed !). At next BP impulse, P2 close and the counting stop. The number stored inside N1 is in fact the time length between two BP impulses.

The sequence timer “copy” the number stored in N1 to N2, after this resets counter N1. When BP becomes low level, N1 restarts the counting. In the same time, the up/down counter N2, starts counting the impulses having 0.5 mS period, which comes via gate P1. It counts down, but with double speed. In this way the counter N2 reach to “0” after T/2 time. The counter N4 and gate P5 makes the impulses for supplementary sparks (2 mS length).

This counter works only if INH signal is at low level. The fip-flop FF1 “marks” the interval T/2 in which will be generated supplementary sparks. It is reseted when N2 reach “0”. The gates P3 and P4 unlock the flio-flop and start supplementary sparks. Also, these gates switch-off the multi-spark function when engine speed limit is reached (in this case, ~ 2000 rpm). How works this ? In the upper table we can see at about 2000 rpm, the time length between two BP impulses is 15 mS.

This means as after a counting cycle, the first 4 bits of counter N1 will be 111 and next 4, 0000. In this case, P3 gate output will be at low level, and the same value for P4 output. The flip-flop FF1 will be not set, and as result, no supplementary sparks. If the speed engine decrease (time length T increase), the last 4 bits of N1 will have at least one 1 and the flip-flop will be set. This allow to appear supplementary sparks until flip-flop will be reseted by borrow impulse of N2.
The module can be maked like a plug-in adapter for an EID.

Description

The circuit is drawn with PCB 123 which you can download for free from http://www.pcb123.com

As a keen cyclist I am always looking for ways to be seen at night. I wanted something that was a novelty and would catch the motorists eye. So looking around at my fellow cyclists rear lights, I came up with the idea of ‘NITE-RIDER’. NINE extra bright LED’s running from left to right and right to left continuously. It could be constructed with red LEDs for use on the rear of the bike or white LED’s for an extra eye catcher on the front of the bike.

All IC’s are CMOS devices so that a 9V PP3 battery can be used, and the current drawn is very low so that it will last as long as possible.

Parts

How it works

IC4, C1, R1 and R2 are used for the clock pulse which is fed to both the counters IC2 and IC3 Pin 14.

IC1 is a Flip Flop and is used as a switch to enable ether IC2 or IC3 at pin 13.

IC7a detects when ether IC2 or IC3 has reached Q9 of the counter pin 11.

IC5, IC6 and IC7a protects the outputs of the counters IC2 and IC3 using OR gates which is then fed to the Anodes of the LED’s 1 to 9.

This circuit uses the popular and easy to find LM3914 IC. This IC is very simple to drive, needs no voltage regulators (it has a built in voltage regulator) and can be powered from almost every source.

Description

When the test button is pressed, the Car battery voltage is feed into a high impedance voltage divider. His purpose is to divide 12V to 1,25V (or lower values to lower values). This solution is better than letting the internal voltage regulator set the 12V sample voltage to be feed into the internal voltage divider simply because it cannot regulate 12V when the voltage drops lower (linear regulators only step down).

Simply wiring with no adjust, the regulator provides stable 1,25V which is fed into the precision internal resistor cascade to generate sample voltages for the internal comparators.  Anyway the default setting let you to measure voltages between 8 and 12V but you can measure even from 0V to 12V setting the offset trimmer to 0 (but i think that under 9 volt your car would not start). There is a smoothing capacitor (4700uF 16V) it is used to adsorb EMF noise produced from the ignition coil if you are measuring the battery during the engine working. Diesel engines would not need it, but i’m not sure. If you like more a point graph rather than a bar graph simply disconnect pin 9 on the IC (MODE) from power. The calculations are simple (default)

For the first comparator the voltage is : 0,833 V corresponding to 8 V
* * * * * voltage is : 0,875 V corresponding to 8,4 V
…
…
for the last comparator the voltage is : 1,25 V corresponding to 12 V

Have fun, learn and don’t let you car battery discharge… 😉

The limitation of car supply voltage (12V) forces to convert the voltages to higher in order to power audio amplifiers.

In fact the max audio power x speaker (with 4 ohm impedance) using 12V is (Vsupply+ – Vsupply-)^2/(8*impedance) 12^2/32 = 4.5Watts per channel, that is laughable…

For powering correctly an amplifier the best is to use a symmetric supply with a high voltage differential. for example +20 – -20 = 40Volts in fact 40^2/32 = 50 Watts per channel that is respectable.

This supply is intended for two channels with 50W max each (of course it depends on the amplifier used). Though it can be easily scaled up or the voltages changed to obtain different values.

Overview – How it works

It is a classic push-pull design , taking care to obtain best symmetry (to avoid flux walking). Keep in mind that this circuit will adsorb many amperes (around 10A) so take care to reinforce power tracks with lots of solder and use heavy wires from the battery or the voltage will drop too much at the input.

The transformer must be designed to reduce skin effect, it can be done using several insulated magnet wire single wires soldered together but conducting separately. The regulation is done both by the transformer turn ratio and varying the duty cycle. In my case i used 5+5 , 10+10 turns obtaining a step up ratio of 2 (12->24) and downregulating the voltage to 20 via duty cycle dynamic adjust performed by the PWM controller TL494.

The step-up ratio has to be a little higher to overcome diode losses, winding resistance and so on and input voltage drop due to wire resistance from battery to converter.

Transformer design

The transformer must be of correct size in order to carry the power needed, on the net there are many charts showing the power in function of frequency and core size for a given topology. My transformer size is 33.5 mm lenght, 30.0 height and 13mm width with a cross section area of 1,25cm^2, good for powers around 150W at 50khz.

The windings , especially the primary must be heavy gauged, but instead of using a single wire it is better to use
multiple wires in parallel each insulated from the other except at the ends. This will reduce resistance increase due to skin effect. The primary and secondary windings are centertapped, this means that you have to wind 5 turns, centertap and 5 windings again. The same goes for the secondary, 10 turns, centertap and 10 turns again.

The important thing is that the transformer MUST not have air gaps or the leakage inductance will throw spikes on the switches overheating them and giving a voltage higher than expected by turn ratio prediction, so if your voltage output (at fully duty cycle) is higher than Vin*N2/N1 – Vdrop diode, your transformer has gap (of course permit me saying you that you are BLIND if you miss it), and this is accompanied with a drastical efficiency reduction. Use non-gapped E cores or toroids (ferrite).

Output diodes, capacitors and filter inductor

For rectification i preferred to use shottky diodes since they have low forward voltage drop, and are incredibly fast.
I used the cheap 1N5822, the best alternative for low voltage converters (3A for current capability).

The output capacitors are 4700uF 25V, not very big, since at high frequency the voltage ripple is most due to internal cap ESR fortunately general purpose lytics have enough low esr for a small ripple (some tens of millivolts). Also at high duty cycle they are feed almost with pure DC, giving small ripple. The filter inductor on the secondary centertap furter increases the ripple and helps the regulation in asymmetrical transients.

Power switch and driving

I used d2pak 70V 80A 0.004 ohms ultrafets (Fairchind semiconductor), very expensive and hard to find. In principle any fet will work, but the lower the on-resistance, the lower the on-state conduction losses, the lower the heat produced on the fets, the higher efficiency and smaller the heatsinks needed. With this fets i am able to run the fets with small heatsinks and without fan at full rated power (100W) with an efficiency of 82% and perceptible heating and with small heating at 120W (some degrees) (the core starts to saturate and the efficiency is a bit lower, around 75%)

Try to use the lowest resistance mosfet you can put your dirty hand 🙂 on or the efficiency will be lower than rated and you will need even a small fan. The fet driver i used is the TPS2811P, from Texas instruments, rated for 2A peak and 200ns. Is important that the gate drive is optimized for minimal inductance or the switching losses will be higher and you risk noise coupling from other sources. Personally i think that twisted pair wires (gate and ground/source) are the best to keep the inductance small. Place the gate drive resistor near the Mosfet, not near the IC.

Controller

I used the trusty TL494 PWM controller with frequency set at around 40-60 Khz adjustable with a potentiometer. I also implemented the soft start (to reduce powerup transients). The adjust potentiometer (feedback) must be set to obtain the desired voltage. The output signals is designed with two pull-up resistors on the collector of the PWM chip output transistor pulling them to ground each cycle alternatively. This signal is sent to the dual inverting MOSFET driver (TPS2811P) obtaining the correct waveform.

Power and filtering

How i said before the power tracks must be heavy gauged or you will scarify regulation (since it depends of transformer step up ratio and input voltage) and efficiency too. Don’t forget to place a 10A (or 15A) fuse on the input because the car batteries can supply very high currents in case of shorts and this will save you face from a mosfet explosion in case of failture or short, remember to place a fuse also on the battery side to increase the safety (accidental shorts->fire, battery explosion, firemen, police and lawyers around). Input filtering is important, use at least 20000uF 16V in capacitors, a filter inductor would be useful too (heavygauged) but i decided to leave it..

Final considerations

This supply given me up to 85% efficiency (sometimes even 90% at some loads) with an input of 12V because i observed all these tricks to keep it functional and efficient. An o-scope would be useful, to watch the ripple and gate signals (watching for overshoots), but if you follow these guidelines you will avoid these problems.

The cross regulation is good but keep in mind that only the positive output is fully regulated, and the negative only follows it. Place a small load between the negative rail and ground (a 3mm led with a 4.7Kohm resistor) to avoid the negative rail getting lower then -20V. If the load is asymmetric you can have two cases:

• More load on positive rail-> no problems, the negative rail can go lower than -20V, but it is not a real issue for an audio amplifier.
• More load on negative rail-> voltage drop on negative rail (to ground) especially if the load is only on the negative rail.

Fortunately audio amplifiers are quite symmetrical as a load, and the output filter inductor/capacitors helps to maintain the regulation good during asymmetrical transients (Basses).

FOR FIRST TESTING USE A SMALL 12V power supply and use resistors as load monitoring switches heat and current consumption (and output) and try to determine efficiency, if it is higher then 70-75% you are set, it is enough. Adjust the frequency for best compromise between power and switching losses, skin effect and hysteresis losses

Bill Of Materials
=================
Design: 12V to 20V 100W DC-DC conv
Doc. no.: 1
Revision: 3
Author: Jonathan Filippi
Created: 29/04/05
Modified: 18/05/05

Parts List
— ——— —–
Resistors
———
2   R1,R2 = 10
4   R3,R4,R6,R7 = 1k
1   R5 = 22k
1   R8 = 4.7k
1   R9 = 100k

Capacitors
———-
2   C1,C2 = 10000uF
2   C3,C6 = 47u
1   C4 = 10u
3   C5,C7,C14 = 100n
2   C8,C9 = 4700u
1   C12 = 1n
1   C13 = 2.2u

Integrated Circuits
——————-
1   U1 = TL494
1   U2 = TPS2811P

Transistors
———–
2 Q1,Q2 = FDB045AN

Diodes
——
4   D1-D4 = 1N5822
1   D5 = 1N4148

Miscellaneous
————-
1   FU1 = 10A
1   L1 = 10u
1   L2 = FERRITE BEAD
1   RV1 = 2.2k
1   RV2 = 24k
1   T1 = TRAN-3P3S

Description

This is a really useful instrument for your car. It uses three LED’s to give a visual indication of the state of charge of your car battery. When the red LED is on the battery voltage is low, green is the OK signal and orange is a warning that the battery is overcharging. The whole circuit is accommodated on a small p.c. board and can be fitted easily anywhere in the dashboard.

Specifications

• Working voltage: 12 V DC
• Max. current: 40 mA

How it works

The principle behind the circuit is very simple. The first LED D1, is connected in series with R2 and D4 and will light when the battery voltage is below 11.5 V. If the voltage is above 12 V the zener Z3 will bias the transistor TR1 sufficiently to turn it on and this will light the second LED D2 which is green and indicates that the battery voltage is normal. As the collector to emitter voltage drop is less than the forward voltage drop of D4 the first LED does not get sufficient voltage across it to light and is turned off. If now the battery voltage rises above 13.5 volts then in a similar way the transistor TR2 is turned on and the third LED lights to indicate potential trouble. The zener diodes are used to provide the reference voltages for greater accuracy.

Schematic

Parts