Lights-On Warning Chime
June 23-24, 2007
 Chaos on the Kissel kitchen table — prototyping the lights-on warning chime. Listen to the sound of the chine. |
More than once now he has walked away from Penny in a parking lot with her lights on. Lynn did not realize how dependent he had become on the lights-on warning that is built into the electronics of modern cars. Penny needs a lights-on warning circuit.
A quick search of the Internet turns up several circuit designs that should work. Lynn focuses on a circuit by Matthew Hunt.
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A diagram of the final circuit (left) is implemented on a prototyping board (right).
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A modification of Matthew's circuit is needed for Lynn's application. With Penny's 6 VDC power supply and the voltage drop across transistor Q1, there is insufficient voltage to properly operate the electronic chime. The chime makes noise, but it sounds more like a sick cow or a broken fog horn. Lynn adds a 5 VDC NO reed relay to turn on the chime. Now the chime sees a full 6 VDC power supply and it happily makes a pleasing "ding-dong" sound.
After successfully debugging the circuit on a prototyping board, Lynn solders the components to a PC board mounts the whole contraption in a project box. Lynn adds some mounting ears to the project box, bolts it under the dash board and connects it to Penny's wiring.
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The completed warning chime. Three connections are made from the terminal lugs on the box
to the car wiring: park lights power; accessory power; ground.
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The circuit works great and has a pleasant tone. The only thing that Lynn would change is the binding posts that he installed on the project box. He is concerned that the connections will loosen with time. If he had to do it again, he would install a three conductor Molex connector instead.
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with your comments or questionsCopyright © 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Lynn Kissel
Last updated: May 24, 2009