Silicon ChipSimple Low-Voltage Speed Controller - January 1994 SILICON CHIP
  1. Outer Front Cover
  2. Contents
  3. Publisher's Letter: Some Australian companies still do not give good service
  4. Book Store
  5. Feature: The World Solar Challenge by Brian Woodward
  6. Feature: Electronic Engine Management; Pt.4 by Julian Edgar
  7. Project: 40V 3A Variable Power Supply; Pt.1 by John Clarke
  8. Order Form
  9. Feature: Luxman A-371 Amplifier & D-351 CD Player by Leo Simpson
  10. Feature: Active Filter Design For Beginners by Elmo Jansz
  11. Project: A Switching Regulator For Solar Panels by Otto Priboj
  12. Project: Printer Status Indicator For PCs by Darren Yates
  13. Project: Simple Low-Voltage Speed Controller by Darren Yates
  14. Vintage Radio: Realism realised - the Precedent console receiver by John Hill
  15. Serviceman's Log: It was all a long time ago by The TV Serviceman
  16. Feature: Computer Bits by Darren Yates
  17. Back Issues
  18. Feature: Remote Control by Bob Young
  19. Project: Control Stepper Motors With Your PC by Marque Crozman
  20. Review: Kenwood's DCS-9120 Oscilloscope by John Clarke
  21. Product Showcase
  22. Notes & Errata: Solar-Powered Electric Fence, April 1993; UHF Remote Switch, December 1989 & August 1990
  23. Market Centre
  24. Advertising Index
  25. Outer Back Cover

This is only a preview of the January 1994 issue of Silicon Chip.

You can view 29 of the 96 pages in the full issue, including the advertisments.

For full access, purchase the issue for $10.00 or subscribe for access to the latest issues.

Articles in this series:
  • Darwin To Adelaide On Solar Power (October 1993)
  • Darwin To Adelaide On Solar Power (October 1993)
  • The World Solar Challenge (November 1993)
  • The World Solar Challenge (November 1993)
  • The World Solar Challenge (January 1994)
  • The World Solar Challenge (January 1994)
Articles in this series:
  • Electronic Engine Management; Pt.1 (October 1993)
  • Electronic Engine Management; Pt.1 (October 1993)
  • Electronic Engine Management; Pt.2 (November 1993)
  • Electronic Engine Management; Pt.2 (November 1993)
  • Electronic Engine Management; Pt.3 (December 1993)
  • Electronic Engine Management; Pt.3 (December 1993)
  • Electronic Engine Management; Pt.4 (January 1994)
  • Electronic Engine Management; Pt.4 (January 1994)
  • Electronic Engine Management; Pt.5 (February 1994)
  • Electronic Engine Management; Pt.5 (February 1994)
  • Electronic Engine Management; Pt.6 (March 1994)
  • Electronic Engine Management; Pt.6 (March 1994)
  • Electronic Engine Management; Pt.7 (April 1994)
  • Electronic Engine Management; Pt.7 (April 1994)
  • Electronic Engine Management; Pt.8 (May 1994)
  • Electronic Engine Management; Pt.8 (May 1994)
  • Electronic Engine Management; Pt.9 (June 1994)
  • Electronic Engine Management; Pt.9 (June 1994)
  • Electronic Engine Management; Pt.10 (July 1994)
  • Electronic Engine Management; Pt.10 (July 1994)
  • Electronic Engine Management; Pt.11 (August 1994)
  • Electronic Engine Management; Pt.11 (August 1994)
  • Electronic Engine Management; Pt.12 (September 1994)
  • Electronic Engine Management; Pt.12 (September 1994)
  • Electronic Engine Management; Pt.13 (October 1994)
  • Electronic Engine Management; Pt.13 (October 1994)
Items relevant to "40V 3A Variable Power Supply; Pt.1":
  • 40V 3A Variable Power Supply PCB pattern (PDF download) [04202941] (Free)
Articles in this series:
  • 40V 3A Variable Power Supply; Pt.1 (January 1994)
  • 40V 3A Variable Power Supply; Pt.1 (January 1994)
  • 40V 3A Variable Power Supply; Pt.2 (February 1994)
  • 40V 3A Variable Power Supply; Pt.2 (February 1994)
Items relevant to "A Switching Regulator For Solar Panels":
  • 72W Switching Regulator for Solar Panels PCB pattern (PDF download) (Free)
Items relevant to "Printer Status Indicator For PCs":
  • DOS software for the Printer Status Indicator (Free)
  • Printer Status Indicator PCB patterns (PDF download) [06101941/2, 07101941] (Free)
Items relevant to "Simple Low-Voltage Speed Controller":
  • Simple Low-Voltage Speed Controller PCB pattern (PDF download) [09111931] (Free)
Items relevant to "Computer Bits":
  • Games Card Breakout PCB [07103941] (PCB Pattern, Free)
  • DOS software for Computer Bits, November 1993 & January/February 1994 (Free)
Articles in this series:
  • Experiments For Your Games Card (January 1992)
  • Experiments For Your Games Card (January 1992)
  • Computer Bits (November 1993)
  • Computer Bits (November 1993)
  • Computer Bits (January 1994)
  • Computer Bits (January 1994)
  • Computer Bits (February 1994)
  • Computer Bits (February 1994)
  • Computer Bits (April 1994)
  • Computer Bits (April 1994)
Articles in this series:
  • Remote Control (October 1989)
  • Remote Control (October 1989)
  • Remote Control (November 1989)
  • Remote Control (November 1989)
  • Remote Control (December 1989)
  • Remote Control (December 1989)
  • Remote Control (January 1990)
  • Remote Control (January 1990)
  • Remote Control (February 1990)
  • Remote Control (February 1990)
  • Remote Control (March 1990)
  • Remote Control (March 1990)
  • Remote Control (April 1990)
  • Remote Control (April 1990)
  • Remote Control (May 1990)
  • Remote Control (May 1990)
  • Remote Control (June 1990)
  • Remote Control (June 1990)
  • Remote Control (August 1990)
  • Remote Control (August 1990)
  • Remote Control (September 1990)
  • Remote Control (September 1990)
  • Remote Control (October 1990)
  • Remote Control (October 1990)
  • Remote Control (November 1990)
  • Remote Control (November 1990)
  • Remote Control (December 1990)
  • Remote Control (December 1990)
  • Remote Control (April 1991)
  • Remote Control (April 1991)
  • Remote Control (July 1991)
  • Remote Control (July 1991)
  • Remote Control (August 1991)
  • Remote Control (August 1991)
  • Remote Control (October 1991)
  • Remote Control (October 1991)
  • Remote Control (April 1992)
  • Remote Control (April 1992)
  • Remote Control (April 1993)
  • Remote Control (April 1993)
  • Remote Control (November 1993)
  • Remote Control (November 1993)
  • Remote Control (December 1993)
  • Remote Control (December 1993)
  • Remote Control (January 1994)
  • Remote Control (January 1994)
  • Remote Control (June 1994)
  • Remote Control (June 1994)
  • Remote Control (January 1995)
  • Remote Control (January 1995)
  • Remote Control (April 1995)
  • Remote Control (April 1995)
  • Remote Control (May 1995)
  • Remote Control (May 1995)
  • Remote Control (July 1995)
  • Remote Control (July 1995)
  • Remote Control (November 1995)
  • Remote Control (November 1995)
  • Remote Control (December 1995)
  • Remote Control (December 1995)
Items relevant to "Control Stepper Motors With Your PC":
  • DOS software for Stepper Motor Control (Free)
  • Stepper Motor PC Interface PCB pattern (PDF download) [07201941] (Free)
If you need a low-cost speed control or low-voltage light dimmer then take a look at this little circuit. It uses just one IC & will control 12V DC motors or lights with rated currents of up to 1 amp. By DARREN YATES A simple low-voltage speed controller If you make your own PC boards, then no doubt you own one of those small PC board drills. These call for an external 12V DC supply capable of delivering at least 1A. With a supply of this rating, the drill will run at about 10,000 RPM. However, you don’t always want to run the drill at full speed and so ideally you need a variable power supply. This simple circuit will do the job efficiently and at low cost. It uses only a handful of components and will comfortably control DC motors rated up to 1A. It is a switching circuit which delivers bursts of current to the motor to provide an efficient means of varying the speed. The circuit can also be used to dim 12V lights and, in fact, its principle of operation is the same as used in the 50  Silicon Chip dimmers for automotive dashboard lamps. Circuit diagram As you can see in Fig.1, the Mini Drill Speed Controller uses very few components and only one IC – a CMOS 555 timer. The 10kΩ and 5.6kΩ resistors, along with the 0.1µF capacitor at pins 2 and 6, set the output frequency of the 555 to about 6.8kHz, although this will vary according to the speed setting. The duty cycle of the pulse output at pin 3 is set by VR1 which has its wiper connected to the control input (pin 5). The higher the control voltage to pin 5 of IC1, the higher the duty cycle and visa versa. The output signal is taken from pin 3 and drives Darlington transistor Q1 via a 1kΩ resistor. Q1 in turn drives the drill motor while diode D2 prevents Q1 from being damaged due to the back-EMF generated each time the motor switches off. The voltage supply to the 555 IC is regulated to 9.1V by zener diode ZD1 and its associated a 220Ω limiting resistor. While the 555 is fairly tolerant of supply variations, the zener diode and its accompanying 10µF filter capacitor are desirable to filter out hash and spikes which can be generated by the motor’s commutator. A 330µF capacitor at the supply input provides extra fil­tering, while diode D1 protects the circuit against incorrect supply polarity. Construction All of the components for the Mini Drill Speed Controller are installed D1 1N5404 220  10 16VW ZD1 9.1V 400mW MOTOR D2 1N4004 10k 4 8 7 5.6k 6 1k 3 IC1 LMC555 2 C B 1 Q1 BD679 E SPEED VR1 10k 5 12VDC 1A PLUG-PACK 330 25VW M D & K WILSON ELECTRONICS PLASTIC SIDE 0.1 E CB MINI PCB DRILL SPEED CONTROLLER Fig.1: the circuit uses 7555 timer IC1 to drive transistor Q1 & this pulses the motor on & off at a frequency of about 6.8kHz. VR1 controls the width of the output pulses on pin 3 of IC1 to set the speed of the motor. The circuit can control 12V DC motors rated up to 1A. on a small PC board measuring 61 x 43mm and coded 09111931. Before you begin any assembly work, check the board carefully for any shorts or breaks in the tracks by comparing it with Fig.3. If you do find any faults, fix them before proceeding further. Once the board has been checked, you can begin construction by installing the wire link, followed by the resistors, the diodes, capacitors and the IC. Follow the overlay wiring diagram to make sure that they are correctly located – see Fig.2. The transistor needs to be fitted with a small heatsink. The 10kΩ pot is a miniature 16mm type which solders directly to the board. If you prefer, you can use one of the larger types with some flying leads to the lid of a box for easier control. Before you hook up your 12V motor or lamp, apply power to the circuit and measure the current drain with your multimeter switched to amps. PARTS LIST 1 PC board, code 09111931, 61 x 43mm 1 miniature TO-126/220 heatsink 1 10kΩ 16mm potentiometer (VR1) Semiconductors 1 LMC555/7555 CMOS timer (IC1) 1 BD679 NPN Darlington transistor (Q1) 1 1N5404 3A diode (D1) 1 1N4004 rectifier diode (D2) 1 9.1V 400mW zener diode (ZD1) Capacitors 1 330µF 25VW PC electrolytic 1 10µF 16VW PC electrolytic 1 0.1µF 63VW MKT polyester Resistors (0.25W, 1%) 1 10kΩ 1 1kΩ 1 5.6kΩ 1 220Ω TO MOTOR 10uF IC1 LMC555 VR1 ZD1 1 2/87a Queen St, St Marys, NSW 2760. Phone (02) 833 1342 Fax (02) 673 4212 When switched on and with no load connected, the circuit should consume about 15mA or so. If this is OK, connected up a small 12VDC motor or lamp and adjust the control. You should see the motor speed or globe brightness vary as you turn the pot. The choice of case for the project is left up to you. You could install it inside a small zippy case or diecast SC box. 330uF D2 5.6k 10k 220  Have you found those components yet? We know that it can be difficult, frustrating and a waste of your valuable time. So why haven’t you contacted us? We specialise in hunting down and locating components – old, obsolete, leading edge, normally available but now scarce due to allocation by overseas manufacturers. Integrated circuits, resistors, capacitors, transistors, diodes, valves, varistors, etc. Any brands Let us save your valuable time Contact us now on 833 1342 We are also distributors for Electrolube lubricants and chemi­cals Hakko - desoldering & soldering irons; SMD tools; replacement parts NTE - replacements semiconductors 1k Q1 D1 12V PLUGPACK 0.1 Fig.2: install the parts on the PC board exactly as shown in this layout diagram. Fig.3: check your PC board against this fullsize pattern before mounting any parts. January 1994  51