Fullscreen HTML5Med Res (??MB)HTML4

I would prefer to leave the existing control in place. Looking at the circuit, it seems as though I could equally reduce the value of the 1kW resistor in series with the 47μF non-polarised capacitor. Can I reduce the value of that 1kW resistor to 470W (or even less) without affecting the audio quality too much? (P. W., Pukekohe, New Zealand) ● Yes, that 1kW resistor can be reduced in value to increase the overall gain. The 47μF capacitor in series with it would need to increase in Advertising Index Altronics.................................25-28 Blackmagic Design....................... 7 Dave Thompson........................ 103 Emona Instruments.................. IBC Hare & Forbes............................... 9 Jaycar..................IFC, 11, 44-45, 53 Keith Rippon Kit Assembly....... 103 Lazer Security........................... 103 LD Electronics........................... 103 LEDsales................................... 103 Microchip Technology.............OBC Mouser Electronics....................... 3 OurPCB Australia........................ 10 PCBWay......................................... 5 PMD Way................................... 103 SC Battery Checker................... 100 SC Christmas Decorations......... 79 SC USB-C Power Monitor......... 103 SC Vintage Radio on USB........... 97 Silicon Chip Binders.................. 67 Silicon Chip PDFs on USB......... 71 Silicon Chip Shop...........92-93, 98 Silicon Chip Subscriptions........ 52 The Loudspeaker Kit.com............ 8 Wagner Electronics..................... 91 Errata and on-sale date 433MHz Transmitter, April 2025: Fig.3 on page 74 has the pin labels DATA and VCC transposed. The PCBs supplied are labelled correctly. Next Issue: the November 2025 issue is due on sale in newsagents by Monday, October 27th. Expect postal delivery of subscription copies in Australia between October 24th and November 12th. 104 Silicon Chip value proportionally to maintain low frequency (bass) response. So if you reduce the 1kW resistor to 470W, you would change the 47μF non-polarised capacitor be 100μF. Note that increasing the gain will increase the noise from the preamplifier. Transistor-controlled Ignition system wanted I am wondering if there is a Silicon Chip magazine project or circuit of a TCI (transistor controlled ignition) module that goes on an ignition coil for a basic lawnmower type magneto circuit (without a 12V battery – not a CDI system). This would be for a twostroke Victa Powertorque mower. I can see CDI projects in 2008 and 2012, but my understanding is the TCI module that triggers firing the spark plug is quite different. It has no capacitors inside, using just transistors and resistors. Some Googling revealed a patented ignition coil TCI module from some company called Atom Industries in 1979 to replace a breaker points system. There is a magnet on the flywheel and it obviously passes the iron core on the ignition coil and induces a voltage in the primary circuit. Then I believe the voltage goes from the primary coil to the silver TCI box that has a transistor circuit that triggers the circuit, feeding voltage to the secondary windings and on to spark plug for firing. Basically, that TCI box replaces the old points breaker system. (E. M., Kew, Vic) ● As far as we can tell, these ignitions originally used points. They charged the coil via the flywheel magnets and closed the points, then fired the ignition when the points opened. They were thus a mixture of Kettering and magneto ignition systems. Instead of the points, they now use a trigger coil and flywheel magnets with either a CDI circuit or a transistor trigger, like the reverse-engineered Atom circuit at siliconchip.au/link/ac76 Our article on Replacement CDI Module for Petrol Motors (May 2008; siliconchip.au/Article/1820) described how it works for CDI versions, but it required a separate trigger coil. The Atom transistor unit appears to use the primary winding of the ignition coil as the trigger coil. The reverse-­ engineered circuit linked above should work for your lawnmower. Australia's electronics magazine We haven’t published such a circuit ourselves. Fixing an old-style remote control Years ago, I built the Studio Remote Control Preamp (September-November 1993; siliconchip.au/Series/168). The third-party remote control has now forgotten its programming. I bought the kit from Jaycar (Cat KC5142) but they no longer have info on the kit in their system and were not able to help. I’m writing in the hope that someone may still have an operational remote for the preamp kicking around and may be able to re-program mine for me, or if there is some other method you may know that I could use to reprogram it. Although the remote that came with the kit was third party, the instructions included a circuit design for a remote based around the MV500 Plessey semiconductor, as the kit uses the MV601 receiver. I don’t think the MV500 is still readily available, but if I am wrong, please let me know. (M. S., Melbourne, Vic) ● The remote control for the Studio Remote Control Preamplifier used the Plessey remote control set of chips: the SL486 receiver and MV601 IR decoder for the receiver, and the MV500 for the remote unit. The MV500 also requires a 500kHz crystal or ceramic resonator, such as the Murata CSB500E, and a transistor or Mosfet to drive the infrared LED. The receiver requires a photodiode as well. The problem could be with any one of these, or some other component. Typically, the universal remote controls that are now available do not support the Plessey infrared coding scheme. It is an outdated method of infrared control using high-current, brief IR pulses. It may be that the remote control is operating and the receiver is faulty. Perhaps you could test the remote using an oscilloscope on the receiver, looking at the signal across the infrared diode and the pin 8 output of the SL486. You can probably make a suitable remote control transmitter using the MV500 and the switches on the remote that are there already. The MV500 and associated parts are available on eBay; for example, see www.ebay.com/ SC itm/323654716404 siliconchip.com.au