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IR touch dimmer zapped by fluorescentsI've recently assembled the Touch Dimmer project from the January & February 2002 issues. It operates well but its behaviour is affected by the switching off of any fluorescent light in the house. Whenever a fluorescent light is switched off, it will switch off the light that's controlled by the dimmer or change to an oscillating mode where the light fluctuates between different levels of brightness. Can you suggest a remedy. (A. C., via email). The problem is probably caused by interference from the fluorescent lights. The interference could be either conducted along the power lines or radiated directly from the fluorescent light to the infrared sensor in the touch light dimmer control. To check where the problem lies, cover the infrared sensor dimmer with an opaque material so it cannot respond to light. If the dimmer is now not affected, then some shielding of the dimmer from the fluorescent lights may be necessary. Repositioning the dimmer in a darker or protected position may be required. Alternatively, remove the infrared sensor (IC2) from the touch lamp dimmer and connect pin 9 of IC1 to pin 5. Check if the fluorescent lights now have an effect. If so, you may require better shielding, particularly from the house wiring. An earthed metal shield behind the dimmer unit may be sufficient to protect it. A .01μF 250VAC (Y class) capacitor connected between the Active and Neutral lines may also help with reducing interference. Thirdly, the fluorescent lights themselves may need a power factor correction capacitor in each fitting. Have these installed by your electrician. The capacitor will act as a power line filter as well as correcting power factor. You may also need to replace the starters in each fluorescent fitting as the suppression capacitor in these may have failed, particularly if the starters are old. Dry cell rejuvenatorWill the dry-cell Battery Rejuvenator from the November 1994 of SILICON CHIP successfully charge "D" size cells? (J. C., Murray Bridge, SA). The circuit should work with D cells although charge time will be a lot longer. It takes around 18 hours to recharge an alkaline AA cell.
Video monitor degaussingOne of the kids put a magnet to the computer screen and it has a green tinge. Can it be fixed? (B. M., via email). The shadow mask in your monitor has evidently become heavily magnetised, so much so that the normal inbuilt degaussing coil may not be capable of fully curing it. You could try turning it on and off several times, leaving at least five minutes between. If that doesn't work you will need to take it to your local serviceman to be degaussed. Battery load testerHas there been a project or article written regarding load testing a car battery or other heavy duty batteries? I have need for a device for testing the condition of heavy duty batteries. Even if a project may not be viable, the methodology for load testing a battery, statistics and figures may be an interesting topic for some. I was prompted for such a device after my car battery of 18 months began to intermittently fail to crank the engine. The NRMA technician, who attended after I eventually determined the battery to be at fault, confirmed my view of a defective battery with a load testing device. I also have a need for a device in the rail preservation scene, with many batteries of unknown quality needing a basic Go/No-go test to determine their future. (R. P., Cowra, NSW). Car battery load testing is usually done with a "carbon pile". Auto-electricians have them. Generally though, you can do a rough and ready test by just turning on all lights; ie, low beam + high beam. A marked drop at the battery terminals indicates a real problem. Testing large storage batteries is more problematic and needs to be done at specified load conditions for the particular battery.
Higher speed setting for PC infrared transceiverHaving recently built the PC Infrared Transceiver from the December 2001 issue, I was wondering what is involved in taking the unit's speed from SIR (115.2kbps), the default setting, to the next higher speed of MIR (1.152Mbps)? Is it a matter of changing external components or is it permanently set by the TFDS4500 transceiver module internals? I realise that this speed was chosen to support all types of Pentium motherboard and the unit works well, but a change in speed would be very welcome as I have a motherboard that supports the higher IR transmission rates. (B. C., via email). Unfortunately, the maximum rate is determined by the TFDS4500 module, which you correctly state at 115.2kbps. We may publish something faster in the future (MIR and/or FIR) but we can't give any guarantees. If you're keen to upgrade soon, you might consider a commercial solution. Microgram Computers often advertise IR add-ons - check them out at www.mgram.com.au Ammeter has stopped workingI recently constructed the 80A Automotive Ammeter from the June 2002 issue and it was working well. However, it now fails to give any correct indication of current levels. When I attempted to re-calibrate the unit at the 'zero' current level, the 'CAL' LEDs light but on removal of the shorting plug, the indication goes to 'OL'. Attempts to calibrate at other levels bring either totally erroneous (high) readings or the 'OL' indication again. The ammeter is an important part of my domestic solar system. I gather it should work satisfactorily in this situation? (R. T., Darbys Falls, NSW). Perhaps there is a short in the Hall effect wiring or the Hall sensor is not working. Check that the Hall effect unit is receiving its 5V supply and that its output is around 2.5V. Alternatively, there may be a problem with the LM358 and associated components. Check its supply and that the output is a varying voltage, indicating that the conversion process is working.
Low fuel warning indicatorIs it possible to modify the Low Fuel Warning Indicator kit (SILICON CHIP, February 1993) so that it can be used as a warning light for low oil pressure instead? The circuit works in conjunction with the fuel sender in the tank and you set the parameters relative to where the gauge is registering, so I was wondering if it was possible to remove the components that create the 10-second delay and use it as a low oil pressure warning light instead. Also would it be versatile enough so that you can select a relatively high oil pressure, say around 20-30 psi? I wouldn't care if it glowed at idle when the oil was hot. I ask this because cars that come with inbuilt gauges on the dash as standard never have an indicator light as well. (B. S., via email). The low fuel indicator can be used for other measurements. The 10kΩ resistor in series with VR1 can be reduced in value if the range is not sufficient. The delay may be reduced but it may still be necessary to have a small delay to prevent false triggering. Use a 10μF capacitor instead of the original 220μF delay capacitor. IR transceiver is possibly damagedI bought the kit to make the IR transceiver published in the December 2001 issue. I tried it out on my Win2000 and it didn't detect it automatically, so I tried to configure it manually and it still didn't work. The circuit has been checked out OK and I would like to know what needs to be done now to get it working. I have enabled IR in BIOS and it is set as IrDa and the Tx Rx stuff is Hi Lo respectively. I don't know if that makes any sense. From your documentation and the stuff I have seen on websites, it should be detected automatically. I downloaded something from Microsoft called IRCOMM, as it was a patch 2000 apparently needed. Currently, I have Service Pack 2 installed and some pre-Service Pack 3 fixes. Your help would be greatly appreciated. (A. M., via email). You should be able to verify that the IR LED inside the TFDS4500 module is not damaged by using your DMM. Switch your DMM to "Diode Test" and measure between pins 1 & 8 of the TFDS4500. With the positive DMM probe on pin 8 and negative probe on pin 1, you should get a reading of about 1.23V. Reverse the leads and you should get no reading (high resistance). You should refer to the "Mailbag" pages in the May 2002 issue
for additional information about motherboard BIOS settings. Microsoft provide
the following general info about irDA setup on Win 2000: How To Configure Your
Computer for Infrared Communication in Windows 2000 (Q302011).
See:
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