Turbo timer alarm override problems

I have installed the Turbo Timer on my car and it works fine except for the alarm override relay switch. When I park the car I take the key and get out. I close the door and press the button on my alarm remote (my alarm is NOT auto-arming). The problem is that it doesn’t always work. When it does, the park-lights flash, the doors lock and the alarm is prepared to go on as soon as the engine shuts down. When it doesn’t work absolutely nothing happens.

It never seems to work if I drive the car only a short distance and is happier if I drive for a longer time. Maybe it needs higher battery voltage or something? Do you have any idea on how I can fix this? Currently, when it doesn’t work I either have to wait around for the Turbo Timer to shut down the motor or I have to switch the car off with the reset switch and then lock up. (F. P., Joondanna WA).

From your description of the problem it seems that the alarm can only be set when the Turbo Timer is running. This is after the engine has warmed up and the thermistor has opened, allowing the Turbo Timer to operate.

You will need to test the alarm with its ignition input disconnected from the ignition output of the Turbo Timer. If your alarm does not operate correctly under these conditions, the alarm connections may be incorrect.

The ignition signal input to your alarm should connect to the 87a terminal of relay RLY1. The second relay RLY2 is only required if the alarm system disables the ignition in some way which would prevent the turbo timer from running the engine with the alarm activated.

Christmas tree LED malfunction

I have just finished constructing the LED Christmas Tree as described in November 1999. One column of LEDs do not light up green although they will light up red. They are LEDs 4, 5, 12, 13, 20, 21, 28 & 29. Can you suggest what I should check to remedy this problem? (Kaye – via email).

 One of the transistor pair, Q7 or Q8, is not doing its switching job. Check your soldering around both transistors and you will probably find you’ve missed doing one or you have a poor solder joint.

Beat-triggered strobe misses the beat I built the Beat-Triggered Strobe Light described in the August 1998 issue. The problem is that it’s not beat triggering well at all. It misses most of the beats and it seems to be a bit behind the beat of the music anyway. I have checked everything over and over again but can not figure out the problem. The oscillation mode was working perfectly until recently as well. Now, when you turn the oscillation control past halfway the Xenon tubes stop flashing but the little test neon is flashing well. When you turn down the oscillation rate, the Xenon tubes start flashing again but not as well as when we first finished it. Please help! (B. W., via email).  The beat input sensitivity needs to be adjusted rather carefully so that the strobe does flash in synchronism with the music. You have not mentioned how you are connecting the line signal inputs to the music source and perhaps the signal is too low which would be indicated by having to turn the sensitivity fully up or clockwise. Alternatively, there may be excessive signal which would be indicated by having to turn the control close to fully anticlockwise. If the signal is too low, you can increase sensitivity by increasing the value of resistance between pins 8 & 9 of IC1a. The existing 47kΩ resistor can be increased to 470kΩ and the .015μF capacitor reduced to .0015μF (1n5). On the other hand, if the signal is too large, you can reduce the signal level before applying it to the line signal inputs on the strobe. Use a series resistor of 470kΩ to reduce the signal by a factor of 10. The problem with the flashing performance not being as good as before could be due to the trigger transformer having a short between windings. Alternatively, you may have arcing between the trigger transformer high tension output and the trigger connections to the Xenon tubes. Check your wiring and separate the high tension wires to the anode and cathode connections to the Xenon tubes. Make sure the mains power is switched off and disconnected and the capacitors are discharged before working on the circuitry. Alternatively, it’s possible that the Xenon tubes are getting old and tired, particularly if they’ve been used a lot. Try replacing them if everything else checks out.

Programmable ignition timing for CDI system

I recently purchased a programmable ignition timing kit (published in June 1999) from Jaycar Electronics in Perth. I’d like to know if this kit is compatible with a Crane Hi-6 multiple spark capacitive discharge unit. I’m running this device in a Holden VK 308 Commodore with electronic ignition and no vacuum advance.

Do I need to make any changes to the circuitry on the ignition timing kit to suit the above system? (S. L., via email).

 The Programmable Ignition Timing module could be used with the Hi-6 unit simply by placing it between the points and the Hi-6 ignition system. You would need to build up the input circuitry for the trigger coil on your distributor. The output from this circuit would then connect to the Programmable Ignition and its output would drive the Hi-6 module which would be set up for a points input.

Details on programming the module for various advance curves were provided in the July 1999 issue of SILICON CHIP.

Timing for slot car drag racing

I have a need to measure times over a few seconds, down to a thousandth of a second, for slot car drag racing. Two lanes need to be timed, false starts indicated and the overall winning car identified at the end of each race.

Can this be done with one of the interface cards designed to be plugged into the parallel port of a computer (I would like to use a notebook computer), or does the card need to do the timing and send the information to the software for display?

If you have published anything which may suit my requirements I would appreciate the information so I can get started. (B. K., via email).

 You are correct in your assumption that the interface card cannot be used for the timing function. However, it could be used to signal false starts, etc to the computer.

The timing could be done with two 74HC390s driven with one section of a 74HC132 configured as an oscillator. Another section could be used to gate the counter. The 16 counter outputs could be switched in two groups of eight to the interface card inputs with 74HC4066 switches.

UHF version of Railpower

Being a model railway enthusiast, it is great to see the Railpower project in the October 1999 issue. I have built many of your model railway projects and found them all very successful. I built your last infrared controller of a few years back and have it working very successfully on my home layout.

Your latest effort seems just as interesting and I look forward to the forthcoming editions to see how things progress. I only have one question and that is would it be possible to have the activation of the controller done by RF rather than infrared? There are RF-activated controllers on the market and these can be a great asset if one is operating layouts at an exhibition. (T. B., Glenroy, Vic).

 Yes, you could use the encoder in the remote to drive a UHF transmitter and then have a UHF receiver in the Railpower. You could base it on the UHF system published in the February 1996 issue.

Garage door controller I have a problem with the Garage Door Controller featured in the April & May 1998 issues. I have completed the controller board and it works fine without a motor connected. I intend using the board to control a sliding gate and have a large, well-made DC motor from an old tape backup system to drive the whole thing. When running with this motor connected, the "up" relay operates normally but when I stop and reverse, the "down" relay produces arcing across the contacts as they are closing. This sends the logic into a total spin and causes the "up" relay to re-engage. It will do this 9 times out of 10, though if I wait for 10 seconds or so before reversing, it will usually operate fine. I am wondering, should I try a windscreen wiper motor to see if the problem disappears? By the way, I have not connected a lamp or the driver transistor (for the lamp) as yet. Would this have any effect? I’ve looked at the supply rails with the CRO; the motor produces some hash but not much. I’ve tried running the relays and motor from a separate supply but this doesn’t work properly. I have also tried various capacitors across the relay contacts and more smoothing on the supply, to no avail. I have also tried running the logic from a 3-terminal 9V regulator while the relays and motor were on a separate 12V battery but this was no good either. (P. W., via email)  We believe your problem hinges around the "large" motor. This means more current than the original design and this may mean that the over-current trip is causing the motor to reverse. The first thing to do is to short out the 0.1Ω resistor from RLY1 to ground. This will prevent the over-current trip from working. If things now work as expected you will have to reduce the value of the resistor by shunting it with one or two 0.1Ω resistors until the gate will close without reversing, unless you put an extra load on it. Alternatively, you may prefer to do away with the over-current limit altogether. One additional thing to watch is the current carrying capacity of the tracks on the PC board. You may have to run thicker wires from point to point on the heavy current tracks. It all hinges on the current that your motor draws. If it is too high, you may also be approaching the limit of the relay contacts.

Radio interference in daytime running lights

I recently built the Daytime Running Lights For Cars as described in the August 1999 issue of SILICON CHIP. It is a brilliant project and works well on my Nissan 4WD wagon. However, I have one problem and that is radio interference.

My favourite radio station that I listen to while driving is the NZ national station which broadcasts on AM at 819kHz and this is seriously degraded while the lighting kit is working. I have tried resetting L1 and even rewound it again but to no avail. I have also thoroughly rechecked the PC board. The problem is readily apparent if the radio is tuned off station on AM and then one can clearly the pulsed power frequency of the Mosfet.

Is there any way I can overcome this problem? (J. N., Tauranga, NZ).

 You should be able to reduce the interference by connecting automotive suppression capacitors across the headlamps and another between the 12V lights supply and chassis. Also a capacitor at the radio supply will help. Best results will be obtained if the antenna for the radio is extended to its fullest. This will give the best signal-to-noise ratio for the radio

Increased power from FM stereo transmitter

I recently bought the FM transmitter published in the October 1988 issue of SILICON CHIP. It works fine but I was wondering if you had any ideas for boosting its output. Do you have any designs for an RF amplifier that can be built onto the output of the BA1404? (P. J., via email).

 We don’t have any suitable RF amplifiers but you can increase the power output by operating the circuit from 3V instead of 1.5V.

Guitar limiter has no attack or delay

I recently built the Guitar Limiter as published in the October 1998 issue. The attack and delay functions don’t have any effect at all although the other functions do work. I can’t see any shorts or misplaced components. I had noticed the component overlay diagram has one of the capacitors not marked. The circuit diagram shows it to be a 1μF electrolytic. Am I correct on that? (D. F., Salisbury, SA).

 The unlabelled electrolytic capacitor on the overlay diagram has a value of 1μF. The only reason that the attack and decay controls would not operate, apart from misplaced components, is that the gain limit control may be set too high or the output level is set incorrectly. Make sure that the output level pot, VR3, is set as per the instructions on page 73.

Railpower model train controller I have two questions about the recent Railpower model trail controller articles. There is no mention in the article as to whether or not you can have two or more controllers on different frequencies. Can this be done? Secondly, why does the controller have an output of 6A. This is totally unnecessary as ALL commercial brands of motor available over the last 20 years at least, draw significantly less than 1A. Even multiple header trains don’t need 6A. I know the maximum output can be lowered by increasing the value of the sensing resister but why design for 6A in the first place? (K. M., via email).  You can have up to four Railpowers on the one layout. All you have to do is use various combinations of links LK1 & 2 on the transmitter and main board, as mentioned in the text on page 80 of the November 1999 article. The Railpower has 6A capacity because it has been used on G scale and large outdoor rail systems that do require high current. We have seen past versions of the Railpower run up to six locomotives in very long trains – that is really something to see. In fact, the Railpower circuit has also been adapted in the past to golf buggies and electric wheel chairs. In any case, our past experience has been that it is better to design for more capacity rather than less. Readers are always wanting to adapt our designs for something bigger, better, etc.

Blackout feature for Discolight

I have built the Discolight as published in the July & August 1988 issues and it works fine. On one of my other light chasers I have a switch called "blackout". It blacks out the power to the lights while keeping everything else running, the indicator LEDs, the chaser sequence, etc. When I want the lights to reactivate, I flip the switch and it continues like nothing has happened.

I have looked in the Discolight but I am unable to exactly relate the part of the circuitry where the switch could be wired in. Can you tell me how to do it? (Peter – via email).

 The easy way to provide a "blackout" feature would be to switch the 240VAC supply to the Triacs. This switch will need to be rated to carry the full load current of the incandescent lamps.

Using the Speed Alert with a vehicle speed sensor

The article on the Speed Alert in the November 1999 issue looks to be a great improvement on the original design published in December 1997. I built the original version but I couldn’t get it to work. It has been in the too-hard basket ever since.

However, I would like to build the new kit and here is my question. Most cars after about 1986 are fuel-injected and most of these have a computer and a VSS (Vehicle Speed Sensor). Some cars run an electronic speedometer as well although many still run a cable speedo. I have a JE Camira which runs a cable-driven speedo but has a VSS wire going into the computer. It would be much easier to hook the Speed Alert up to this wire instead of finding a place to attach magnets and the pickup coil. Could you suggest a simple modification to the sensor section which would allow this? (C. P., via email)

I would like to know if the Speed Alarm published in the November 1999 issue unit could use the electronic speed sensor already mounted in my car’s transmission instead of one fitted to the drive shaft? The sensor was fitted for a VDO monitoring unit along with fuel and other sensors. The VDO unit has now been taken out but the speed sensor is still mounted and has three wires terminating to a Molex plug. (C. S., via email).

 For both of these cases, the installed sensor should be suitable. Just connect the signal wire to the signal input at the free end of the 1kΩ resistor connecting to pin 2 of IC2a.
The calibration procedure remains the same.

Faulty electric fence controller

I have built the High Power Electric Fence Controller as described in the April 1999 issue of SILICON CHIP. At the output the spark jumps across a 5mm gap and gives a loud crack. But attached to fence wire using 60 feet deep bore casing as earth, it is not good. The fence wire is almost dead – I can hold it. My old mains-operated fencer easily handles the task – about half a kilometre.

Please suggest what is necessary to make the unit operational as it is needed for another paddock. (A. C., via email).

 The electric fence controller on its own appears to have sufficient energy as indicated by the loud crack and 5mm spark. The loss must be in the fence run. Note that the electric fence controller does have a very fast risetime for the output pulse and this could be causing one or more of your fence insulators to break down or arc over. This would prevent the fence from delivering the energy when you hold it.

A slower risetime pulse such as from a different controller may not affect the insulators so much. Try it on your new fence run. If the insulators are newer it should work well.

Satellite receiver modification

I have built the Satellite Receiver published in the May, June & July 1995 issues of SILICON CHIP. I have set it up to a point and can’t zero the meter. Apparently the pre-built module has higher gain than the original. What can you suggest? (J. S., via email).

 It should be an easy matter to zero the meter if you follow these procedures carefully. First, measure the AGC voltage connecting to pin 5 of IC2a with respect to ground. Now check that the pin 7 output of IC2a is also this same voltage. The meter is set to zero when the pin 1 voltage from IC2b’s output is identical to the output from IC2a.

If you cannot obtain the correct voltage you may need to change the resistor values on either side of VR6. If the voltage cannot be adjusted low enough, decrease the 1kΩ resistor. If the voltage cannot be set high enough, decrease the 2.2kΩ resistor.
The sensitivity of the meter can be set by using a higher value of resistance for VR5.

Problems with Touch Lamp Dimmer Could somebody please help me out with the Touch Lamp Dimmer published in the June 1989 issue of SILICON CHIP? It doesn’t want to work. I’ve checked everything from shorts to reversed/wrong components. I am wondering if the two high voltage capacitors, ie, 0.1μF 250VAC, would make difference to the overall reference voltage of +5V. I’ve been given two MKT capacitors which are coded 275VAC 103. After cross-checking, I found their value to be .01μF and not 0.1μF. The voltage at pin 1 of IC1 (SLB0586A) is around 3.75V to 3.85V. Would this be the cause of the Triac not switching on? (S. F., via email).  The use of two capacitors that are 10 times smaller than the circuit suggests will affect the operation of the dimmer. C1 is a filter capacitor to reduce electromagnetic interference, while C2 is there to provide the current necessary for the power supply which is derived directly from the mains. Using a value of .01μF will cause the supply to be low in voltage and as you have found, well below the required 5V. Use the correct types and it should operate properly.

Charging 3.6V batteries

I am building your Multi-purpose Fast Battery Charger as described in the February 1998 issue. I would like to be able to charge several other NiMH batteries, in particular 3.6V. Could you please tell me the formula or method used so I can calculate my own resistor requirements? I will be changing SW5 to a 2-pole 8-position switch to accommodate the existing voltages plus three more. (D. E., via email).

 The value of resistance for lower voltage batteries can be calculated knowing the pin 19 input of the TEA1102 requires the equivalent cell voltage of 1.2V. So for a 3.6V battery we would set the resistance divider to divide by 3. The resistance from the positive terminal of the battery is fixed at 100kΩ and it is only the resistance from switch S5a connecting to ground which is altered.

The formula works out as 120kΩ/ (Vbatt-1.2) = resistance value required. If Vbatt is 3.6V, the required resistance is 50kΩ ohm. Two 100kΩ resistors in parallel would be ideal.

Notes and Errata PC Powerhouse, December 1999: if this project is used to drive powered loudspeakers for a PC, you should first check that the ground of the signal line (ie, shield connection) is not connected to the positive supply for the speakers. While we have not encountered this situation, it is not suitable for the PC Powerhouse as it would cause a short circuit to occur across the 5V output.

WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable.