Dust Buster Switch Problem - Page 1
Forum section: electronics / projects

author: calzap
author_rank: Frequent Contributor
timestamp: August 25, 2015, 03:12:26 am
content: Our small hand-held Dust Buster vacuum cleaner developed a flaky switch problem. Sometimes the switch worked if it was moved back and forth a bit and pressed just right. Opened the case hoping to find an easily replaceable switch. No such luck. Switch is part a plastic bus with multiple traces. Switch portion is a set of connected wipers that is supposed to make contact with different traces in the off and on positions. Tried cleaning the traces and wipers, but this did not fix the problem. So, would need to remove the wipers and solder-in wires to a toggle switch (replacing the bus was a nonstarter). See picture.Before a toggle switch could be installed, I needed to understand the circuitry, so a minor tear-down was performed. See the circuit diagram. I was surprised at the crudeness of the battery charging circuit. No full-wave rectification, smoothing cap, voltage regulator, taper-to-a-trickle rubbish; no sireee. Switch mode charger? Not a chance. Use a small, cheap AC wall-wart, half-rectify and drop the voltage with a few cheap diodes, and you're good to go. Batteries will last long enough that the consumer won't be too angry when they fail. Discontinue the model after a couple of years, and you don't have to worry about supplying repair parts either. At least the outputs of the wall wart are isolated from the mains inputs; it probably could not have gotten its UL sticker without that.Original switch wipers were interesting. See the pic. They had soldered an additional thickness of metal at the point of contact on each wiper, presumably to compensate for wear. The traces that the wipers rub had not been beefed-up though. However, surface oxidation and corrosion and loss of springiness developed so rapidly that the extra thickness on the wipers was useless.So, removed the movable switch parts, including the wipers, and soldered wires to the old switch traces. Installed a SPDT toggle switch rated for 10A, and it works OK for now. Also, soldered the motor inputs to the bus. Originally they were just shoved through holes in the bus traces and dependent on friction for electrical continuity. See pics. Should have replaced the charging circuit with something better, but haven't the time now; hopefully real soon.Additional specs:Battery pack is twelve D-SC1500P NiCd's wired in series. For each battery, data sheet specs are 1.2 V with 1300-1500 mAh max output. Wall wart 120 VAC in, 17 VAC, 200 mA out. Motor is Leshi Motor 545S-60938, 14.4 VDC, and is quite a little brute. Draws 10A at most efficient operation, and has a whopping LRA of 50.Mike in California

author: TheElectricChicken
author_rank: Frequent Contributor
timestamp: August 26, 2015, 04:12:13 pm
content: You've done well repairing it and went about it just the same as I would too. Cool. I often have to sketch circuits to understand them, not always, but it sure helps sometimes.looking at my desk, the last thing I drew was the washing machine circuit, but I can't see how the motor is wired herehttps://www.eevblog.com/forum/projects/how-to-wire-this-washing-machine-motor/msg734179/#msg734179I'm glad you got your project working and shared it with everyone. It is good to see how repairs can save you money and the planet too. I prefer repairing or making things rather than buying because you get a more comfortable relationship with the item and know how much you can rely on it (or not). With stuff from the store, you don't know when it will leave you in the lurch.