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Recent Questions

February 2017


Auto Bell Galloping Dominoes

I have an electro-mechanical gambling machine — Galloping Dominoes — from the company Auto Bell, and would greatly appreciate if someone could direct me to where I could find a schematic. It has a motor that turns four large switch cams and three smaller cams, and has numerous multi-pole relays all interconnected. Thanks!

#2171
Randy Grunwell
Suwanee, GA


Radio Whine

I have been using a Sony ICF-9740 AM/FM table radio on my nightstand since 1974. Recently, there is increasing interference on the AM band. It’s not AC “buzz” or “hum” that one would expect from old power supply filter caps; it's more of a high frequency whine — my guess is around 6-8kcs, and it's consistent even when the volume is turned all the way down. I could replace this unit but I would really rather fix it. Any pointers on finding the source of the noise or theories on what might be causing it?

#2172
Radio Whine
Houston, TX


Three-Way LED Flasher

I need a simple circuit to sequentially flash three separate strings of 10 LED lights. Flashing two strings is easy; three is tougher.

#2173
Michael Herman
La Quinta, CA


LED Compatibility?

I replaced some outside 60W bulbs with CREE dimmable LED replacements. The lamps are  controlled and dimmed using X10 switches. When switched off, the lamps still glow at about 20% and will not shut off completely unless I use the disable feature of the switch. However, this prevents the timer from automatically controlling the lights. What causes this and is there a fix, or are LED replacements not compatible with X10?

#2174
Christoffer Mortensen
Piscataway, NJ


Vehicle Detector

Does anyone have suggestions for buying or building a vehicle detector which can be used with the Arduino? I wish to sense and count passing vehicles.

#2175
Robert Johnson
Bolton, MA


January 2017


Uno-Known Device

I’ve used the Arduino IDE with a genuine Arduino Uno board for experiments for a few months without trouble. Recently, I wanted to permanently put an Uno in a desktop project, so I purchased some budget Arduino Uno compatible boards. The budget boards seem fine, but the Arduino IDE doesn’t recognize any of them. When connected, the boards show up as an “Unknown Device.” I am using Windows 7 32-bit. Does anyone have any pointers on how to make this board work?

#1171
Michael Allison
Camden, NJ


Trainsformer Needed

I found a bargain at a local thrift store and now have a 1959 Marklin HO Scale train, cars, and track. The set didn’t come with a transformer, so I thought it would be a fun project to build from scratch. Does anyone have a schematic or suggestion for a DIY train transformer they can share?

#1172
Alfred Thompson
Kingsport, TN


Turn Signal Signal

I have a newly restored 1971 Honda CB350 motorcycle that I ride for fun on the weekends. One problem is forgetting to turn off the turn indicators. I have found a kit that “beeps” every time the indicator lights up, but it's very annoying as I sit at a light. I would like a circuit that would alert me only if the turn indicator stays on for more than two minutes. Schematic would be welcome!

#1173
Leland Collins
Gulfport, MS


How Much Tolerance Is Enough?

When designing circuits, is there a rule of thumb for picking voltages and tolerances of components? For example, if my power source is 12 volts, is an electrolytic capacitor with a 24V rating  “better” than one with a 16V rating? What do good designers use as a margin?

#1174
Enrico Gutiérrez
Panama City, FL


December 2016


Fridge Alert

My young son frequently leaves the fridge door open. I’m an electronics beginner and I’d like to build a simple circuit to alert me when that happens. It should be simple enough that I could build it with the help of my son, so he learns two lessons in one sitting. Schematic and design appreciated!

#12161
Michael Calhoun
Odessa, MO


More Questions