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Advertising Index Altronics.................................. 78-81 Amateur Scientist CD................... 93 Electronex...................................... 9 Embedded Logic Solutions.......... 32 Emona Instruments...................... 71 Geoff Coppa............................... 103 Grantronics................................. 103 Harbuch Electronics....................... 7 Ask SILICON CHIP . . . continued from p100 are new, having been replaced within the past few months. The Light Box Control Timer unit was a faithful replication of that described in SILICON CHIP and when completed performed exactly as described in the article when operated on the bench with no load attached to the relay. However, when installed in the light-box with a fluorescent tube load connected, it began to behave somewhat erratically on start-up. Most of the time it would only generate a mere flicker from the tubes and then nothing. Pressing start again usually had the same outcome, although once in about five times, before the microprocessor became completely confused and displayed random outputs, the lamps would fire and run for their timed period before switching off. Trying to improve the reliability of the start-up has proven frustrating and I have double-checked, tested and virtually rebuilt the controller board in several different configurations to try to isolate and remove the problem, including re-programming the microprocessor. The differing configurations included alternative relays (on and off the PCB), separate input mains power supplies, full suppression of the mains input supply etc. After extended deliberations, I have concluded after testing the relay with both DC loads and other AC loads that the trigger action of the fluorescent starters seems somehow to be applying a power spike into the input circuitry of the 16F84A, shutting down operation almost immediately after it begins, suggesting that some further decoupling of the micro inputs may 104  Silicon Chip DOWNLOAD OUR CATALOG at Hare & Forbes.......................... OBC www.iinet.net.au/~worcom Instant PCBs.............................. 103 WORLDWIDE ELECTRONIC COMPONENTS PO Box 631, Hillarys, WA 6923 Ph: (08) 9307 7305 Fax: (08) 9307 7309 Email: worcom<at>iinet.net.au Jaycar .............................. IFC,49-56 Notes & Errata LED Sales.................................. 103 Mix-it! 4-Channel Mixer, June 2012: Fig.8 on page 67 should show the top switch connecting to signal ground and the bottom switch going to pin 7 of IC1b (not the other way around). Soft Starter for Power Tools, July 2012: the X2 capacitor specified in the parts list is a tight fit on the PCB. Element14 part code 1215460 is a better fit, as is the Altronics R3129. well be in order. I would be grateful if you could provide me with your thoughts and any possible solutions. (W. G., Dunedin, NZ). • The inputs to the PIC are only held high via internal pull-up resistors and these may be too high for an application within a fluorescent tube lighting box. The problem should be solved by adding 10kΩ pull-up resistors between the +5V supply and the RB6 & RB7 inputs. Adding 100nF ceramic capacitors between these inputs and the pin 5 ground supply should shunt any interference to prevent false triggering (see also the errata in March 2012). If this doesn’t cure the problem, the timing board should be shielded from the fluorescent tubes, starters and ballast with an earthed piece of tinSC plate. Keith Rippon............................... 103 Kitstop............................................ 6 Low Energy Developments........ 103 Matrix Multimedia......................... 11 Microchip Technology..................... 3 Mikroelektronika......................... IBC Ocean Controls.............................. 8 Quest Electronics....................... 103 Radio, TV & Hobbies DVD............ 99 Reality Design................................ 7 Red Button Technologies............. 63 RF Modules................................ 104 Sesame Electronics................... 103 Silicon Chip Binders................... 103 Silicon Chip Bookshop............... 102 Silicon Chip Order Form............... 95 Silicon Chip Partshop................... 94 Silicon Chip Subscriptions......... 101 Siomar Battery Engineering.... 5,103 Splat Controls............................. 103 Tekmark Australia........................... 6 Truscotts Electronic World.......... 103 Wiltronics...................................... 10 Worldwide Elect. Components... 104 siliconchip.com.au