I'm not handy at thinking electrical circuits through.
I am looking for the diagram for making a simple buzzer box to warn of short circuits (reversed drop feeders etc.) while working away under the benchwork.
I found this old thread on the topic but the photos have been removed.
http://cs.trains.com/trccs/forums/t/140951.aspx?PageIndex=2
Can anyone post me a simple circuit? I simply want to use a piezo buzzer and 9 V battery I have on hand. I don't need any other functions on the circuit.....LEDs etc. etc.
Thanks to anyone with a diag. to post or written instructions etc.
Hook one wire of the buzzer (9 volt or more) to one terminal of the battery the other wire will go to one rail the other terminal of the battery will go to the other rail. Make sure your DCC system is not connected before connecting the buzzer. I use my multimeter on ohms with the beep enabled. Most multimeter will have a beeping ohms function.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
Actually most digital meters have an option to buzz on short. It's the continuity scale. Just clip the meter to the rails. If you get a short the meter will buzz.
Springfield PA
locoi1sa Hook one wire of the buzzer (9 volt or more) to one terminal of the battery the other wire will go to one rail the other terminal of the battery will go to the other rail. Pete
Hook one wire of the buzzer (9 volt or more) to one terminal of the battery the other wire will go to one rail the other terminal of the battery will go to the other rail. Pete
Duh, on me, Pete.
Thanks. I knew I was taking a risk of seeming a complete ninny, but I had hooked the thing up that way and got a buzz immediately. However, I couldn't see how I had a short circuit already, so I assumed I was hooking up that little circuit in continuous play mode somehow.....well, duh......after hours of checking, (you can guess)............yup, the heat from one drop feeder solder point had melted the tinyest of bare spots on the other feeder below and I had a short....but even pulling the wires out to look at them seemed like there was no problem....had to look again with my high powered drug store specs.
At least now I have the buzzer from here on out.....only 100+ more drop feeders on the rest of the layout expansion.
Whenever you hook any external voltage to the track, even a battery, make sure the DCC system is disconnected. Also take a sheet of paper and write down a reminder and place it on the DCC system. If you have no shorts while working it's easy to forget the battery is hooked up. If you forget and energize the system the battery could overheat and blow.
Hamltnblue Whenever you hook any external voltage to the track, even a battery, make sure the DCC system is disconnected.
Whenever you hook any external voltage to the track, even a battery, make sure the DCC system is disconnected.
Thanks for the reminder. No problem for me at this point. I'm just reconnecting all the track modules of the old layout prior to attaching it to the new expansion. No DCC hooked up yet.....but I can't wait to get the new Digitrax DT402D hooked up via the Zephyr controller and testing out the old layout now that it is almost back together.
It's been 9 months since I took it apart into its modules to move it to the new house. The benchwork is almost complete on the expansion. The roadbed is waiitng to go on. Almost all components are waiting in the garage for the installation time. Photos to follow.
Why a buzzer at all?! Why not a much cheaper 12v auto tail lamp wired in series someplace, or several. Not only do they forestall damage to any decoders or other sensitive electronics, but when they experience the short they light up and tell you exactly where the short is.
-Crandell
Crandell
The OP is just wiring new sections. The buzzer will let him know if there is a short in his wiring as he works under the layout. The tail light bulbs will let him know if there is a short while running the railroad. Soldering feeders should not be done while there is power on the buss. A short while working on the layout may go on for a long time and fry the protection circuit in the DCC system or burn track ties and feeder wires. The buzzer is an audible warning that something is not right. It could be something as simple as something laying across the rails or difficult to find as a hidden reverse loop in a complicated track scheme.
You are right, Pete, although I was implying a solder and test approach with the intent of leaving the bulbs in place after all the electrical work and testing. Do a solder, power up and test with the bulb already installed for that sub, and then power down and move to the next area.
But, thanks for pointing out what it probably seemed as if I hadn't considered. I could have expressed myself more clearly.
You should not have any power on a circuit while you are soldering it. This is especially true if you are using a soldering gun, which is essentially a step down transformer. A step down transformer hooked up backwards is, of course, a step up transformer.
If you get the business end of a soldering gun across a live AC or pulsed DC circuit in just the right way, you will end up with high voltage in the primary. It can be high enough to break down the insulation and jump to the nearest ground via the screws in the handle.
This isn't just theory, I've had it happen to me a couple of times back when I had to solder live circuits due to the nature of the work I did.
A 9 volt buzzer will result in pulsed DC being present on the wires. Granted, that low a voltage fed into the secondary of a soldering gun even under the most favorable conditions, probably won't generate a high enough voltage in the primary windings to break down the insulation. Still, it's bad practice and it shouldn't be done or recommended.
The best thing to do is solder the joint, then do a quick short test before moving on to the next joint.
Recovering former former model railroader.
The 9 volt battery will be fine on the rail while soldering. It would be isolated and there is no reference to the AC of the solder iron.
You'd have to remove the tip from the soldering gun and touch each leg to a rail with the 9V on it AND pull the trigger to turn on the switch to get 120VAC (or more) out of the plug end.
Pretty much not gonna happen by accident, that's for sure.
However, you SHOULD disconnect the track bus from the DCC system and take locos off the track when soldering to the bus or connecting feeders to the track. You CAN get induced voltages as most solderign guns and irons are not isolated or grounded. Battery powered ones are ok (I don;t mean Cold Heat - that too puts voltage on the track and doesn;t solder worth a darn anyway - but rather a rechargeable portable iron like a Wahl Iso-tip). here are grounded irons, usually in the lower wattages, for fine electronics work without damaging components from staic and/or induced voltages - the little 15 watt one I had from Radio Shack was liek this, 3 prong cord and all. Before I got my soldering satation this was what I used to assemble circuit boards and solder the tiny decoder wires and LEDs.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinker You'd have to remove the tip from the soldering gun and touch each leg to a rail with the 9V on it AND pull the trigger to turn on the switch to get 120VAC (or more) out of the plug end.
As I said, a lot of conditions have to be present to get shocked in this manner, but removing the tip isn't one of them. Oxidation and loose tip nuts can take care of that part. And as I also mentioned, a 9 volt source isn't likely to induce high enough voltage to break down the insulation. Still, soldering with any potential applied to the circuit being worked on isn't a good idea.
Lastly, for Hamltnblue, a voltage source present on the circuit being soldered does not have to be referenced to AC power in order to get shocked in this manner.
What I was refering to was the 9 volt battery itself and not gettign shocked. If the 9 volt battery is not referenced to the solder iron it will not be damaged.