IMPORTANT: Milliamps and Voltage for Alarm Boxes

Hello All,

I wanted to share something with all of you, so I can hopefully save some of you the headaches I had.

A few months ago, I acquired a 51 Style Three Fold Box. I then decided to buy a 10' center wind turtle gong. I followed everything to the the letter with respect to not going over 100 milliamps. At the time, I was using a 12 Volt DC power supply, and a 100 ohm resistor, along with one box, and my 10' gong. Everything worked GREAT!

I then acquired another 51 box, and added that to the circuit, used a lower resistance resistor (so I could maintain my 100 milliamps), and things still worked great. I could pull one box, then while the 1st box was still running, I would pull the second box. The 2nd box would wait till the first box was done (like it should...Non-interrupting).

I then added a 3rd box (51 style), went to a lower resistor in order to still maintain my 100 milliamps, and now this is where my problems began! If I pulled the 1st box, then with the 1st box still running, I pulled the 2nd and 3rd boxes, the 3rd box would interrupt the other boxes.

To make a long story short, and with the help of MANY helpful, and friendly fire box collectors, we figured out the problem and solution. I needed to use 24 Volts DC, and of course that forced me to use a larger value resistor (around 200 ohmns), in order to maintain my 100 milliamps. With this new 24 volt confguration. Everything now works GREAT!!!!

Another word of advice. Please put a current meter inline with your box circuit, so you can make sure you are at 100 Milliamps.

Bill
 

Bs918

Firefighter
I think another problem is the fact that for some unknown reason, well I guess I know the reason, people feel compelled to hook up their fire alarm box directly to the turtle gongs or wood cased gongs and pull the box and listen while their ears become perforated.

The purpose of the gong was to alert the firefighters that there was a fire for them to respond to, not to listen while a 10” gong pounded out 4-6-4-9 after it did that a couple of times I would think you would be ready for the Looney bin not a fire.

I realize that many fire departments did things in many different ways, but the Game well Street Box System was not designed to tap out on House Gongs, at least not in Youngstown Ohio, and I have documented that through 1930.
 

almdoc

Firefighter
This is the first time I've looked at this posting because there are a lot of different ways to power your displays. I have a museum alarm display with 3 boxes, a register, oak case gong, and indicator running on 15 vdc at 100 mills. Alarm equipment will operate correctly with as little as 80 milliamps.
There is one very important factor you have forgotten when it comes to non-interfering boxes. All boxes MUST be timed EXACTLY the same. Boxes on 1/2 second timing will not work correctly with boxes timed at 1 second. 1 second timing will not work correctly with 2 second timed boxes etc. etc.
One other thing, if you operate your boxes with inner case doors open you are adding the resistance of the tap bell into the circuit which is dropping the mills. Also, the non-interfering coils are added in when the box is activated.
All these things drop mills when the circuit is sending a signal. 100 mils is the "at rest" milliamps for the circuit. Thats why alarm equipment is designed to operate correctly at a range of milliamps.
 
Can anyone suggest a power supply for me? i have 2 boxes and a house gong, and have a good idea of how to hook them up. But what power supply do I use? Thank You

Toledo Box 396
 

almdoc

Firefighter
Hi,
The easiest way is to buy a radio shack universal ac/dc adapter part #273-028. It's $19.99. Wire it to your stuff in series. ( a loop ) Start with the lowest voltage and work your way up until all your equipment in your display works correctly. Go no further on voltage. It may work on the lowest setting depending on how much you have on your circuit. As you add things you may have to bump it up a notch. I have several museum displays operating this way and have no problems. Maintaining 100 mils is a municipal circuit thing not nessesary for displays. Voltage dictates milliamps so use the lowest voltage that works and you in the ballpark for milliamps. Doc
 

Erie_Gamewell

Firefighter
I have been running my setup based on almdoc's recomendations for a while now and have had no issues. its the easiest way to do it and you dont have to worry about buying and adding resistors to your setup. thanks almdoc.
 

magicitybill

Lieutenant
I purchased a 9V 100ma plug in tansformer on e-Bay for $8.00 including shipping. I did add a 200ma fuse (I could not get a 150ma one) to the circuit. I put the fuse and a small knife switch on a board with some screws for terminals. This runs two boxes and an upright tapper without any problem.
 

gls24

Firefighter
Be careful though. Just because the power supply is rated at 100 mA does NOT mean the circuit will operate at 100 mA. The 100 mA rating on the power supply means that is the maximum that the supply can deliver safely. The current your circuit draws is determined by the voltage at which the supply is operating and the resistance presented by the equipment on your circuit. It IS possible that your circuit will draw more than 100 mA from the supply and cause it to overheat and fail. As mentioned in a post above, fusing the circuit and including an ammeter in the circuit to monitor the current is the safest way to know the current at which your circuit is operating.
 

magicitybill

Lieutenant
Oh. That is good to know but, if the power supply can only supply 100mA how can it supply more? I do not want to test what you say with my boxes. I just wonder. Can you get a 125mA fuse? If I use 100mA fuse do you think it will hold up? I suppose I should put an ammeter in line to answer that. The supply house I got my fuses at did not carry 125mA. It is the old glass cartridge type fuse.

I also have noticed that "people" say that Gamewell equipment will operate on as little as 100mA. Everything I read says not to excede 100mA. Why do I see the "as little as" sometimes? Again I do not want to use anything I have collected to test greater ratings. Just curious. Thanks for your imput!
 

gls24

Firefighter
Most power supplies (unless they are current-limited) will supply more than their rated current. The rating is what the supply can "comfortably" deliver. Most Gamewell equipment will operate below 100 mA....some designed to respond on as little as 60 mA. In fact, the 100 mA operating current for Gamewell circuits is the "at-rest" current. During operation of a box (or boxes) the current can drop as non-interfering coils and tap bells can be in or out of the circuit depending on whether box doors are open or not. In some Gamewell circuits, current was temporarily increased beyond 100 mA to activate telephone relays. These relays were designed NOT to respond to the 100 mA....only to the increased current. I use 250 mA fuses in my circuits. Generally, you need about 10 Ohms resistance per 1 Volt in your circuit. Most boxes (at-rest) present no resistance to the circuit, so if you try to operate ONLY a box, the box will quickly drain the battery or short out the power supply. Equipment such as turtle gongs and registers each present about 30 Ohms to the circuit. So, theoretically, if you place a box, a gong, and a register in a loop, it should operate at close to 100 mA if powered by 6 Volts DC. You can get VERY inexpensive milliammeters from Hong Kong on eBay; get one whose range is 0-200 or 0-300 milliamps.

Remember, current is drawn by a circuit; it is NOT pushed out by the power supply. The current drawn is determined by the voltage in the circuit and the resistance of the circuit.
 

magicitybill

Lieutenant
I have a power supply with resistors, fuse and ammeter in my 2-box, gong, & register circuit. I am using 200mA fuses in both circuits and they have held up. I think that should protect the 2-box and tapper circuit with the plug in power supply. Do you agree?
 

gls24

Firefighter
Yes, I agree. As a result of our discussion here, I did some experimenting. I have some extra coils, so I tried a little experiment. Using a 9 volt battery (that is often suggested as a power supply for testing purposes) and my milliammeter I powered a couple of sets of coils and measured the current. What would happen if I used too high a voltage for the resistance at hand? Actually nothing....no ill effect to the coils...they didn't even get slightly warm. So, not even close to burning out. The first test was with a set of 20 Ohm turtle gong coils. Applying 9 volts, the coils drew 340 milliamps without harm. Second test, I used a set of 17 Ohm sounder coils from the ceramic terminal block from an older box. Applying 9 volts, the sounder coils drew 430 milliamps. They too showed no ill effects and didn't even get slightly warm.

So, the whole point here is NOT to say use whatever voltage you want to use. But rather, don't be overly worried about burning up equipment. Be reasonable with your choice of power supply and shoot for operating your circuits at 100 mA.

BTW, in their central office entrance cabinets, Gamewell used 1/2 Amp (500 mA) fuses to "protect central office equipment". My simple tests seem to bear out 500 mA fuses being an OK value. Since small demo circuits don't have the same potential for variance as municipal circuits, I'd still suggest sticking with the lower 200 or 250 mA fuse.
 

magicitybill

Lieutenant
I put a meter and an ammeter in my 2-box & tapper circuit powered by a plug-in 9V & 100mA transformer. Surprise! It puts out 13V and 175mA. So like Gls24 advised always use an ammeter and be sure!
 
almdoc said:
Hi,
The easiest way is to buy a radio shack universal ac/dc adapter part #273-028. It's $19.99. Wire it to your stuff in series. ( a loop ) Start with the lowest voltage and work your way up until all your equipment in your display works correctly. Go no further on voltage. It may work on the lowest setting depending on how much you have on your circuit. As you add things you may have to bump it up a notch. I have several museum displays operating this way and have no problems. Maintaining 100 mils is a municipal circuit thing not nessesary for displays. Voltage dictates milliamps so use the lowest voltage that works and you in the ballpark for milliamps. Doc
This is the only adapter I found on Radio Shack website. https://www.radioshack.com/products/radioshack-13-5-30-volt-1000ma-ac-adapter

Will this work?
 

gls24

Firefighter
That depends on what you are powering. The lowest voltage setting is only 13.5 volts. That is too much voltage (causing too high a current) for most simple box and bell setups. You need to find a power supply that will provide at least 300 mA current and have voltage settings between 3 and 12 volts. If you are operating just a box and bell, 3 to 6 volts should work. With higher voltage you risk burning coils. Unfortunately, Radio Shack is only a shadow of its former self. So, you'll need to "google" another source.
 
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