Custom Voltage Test Box

Do you make your own test boxes?

Test boxes can be made for a variety of reasons. They are typically home made boxes that help to make manipulating voltage a little more usable for a specific task. They are usually not sold by a manufacturer because the market or target audience is extremely small. There is little to no room for profit to be made.

DC Voltage Box

This is a box that I have made strictly for DC output. If 48VDC or 24VDC voltage is needed, I put a variac on the AC input and adjust the AC voltage until I get the desired DC output. This box utilizes a 2 pole switch, to switch the 120V hot and neutral. The load side of the switch is a 1000V rectifier with a 30A fuse in series between the switch and the 120V rectifier input. This box is a Radioshack plastic project box with a steel decorative finish plate.

Resistor Box

The purpose of this box was to help identify bus duct phases. When you have a 7 story bus duct riser, and your task for the day is to test the bus duct by your self, part of testing involves phase identification. Bus ducts typically aren’t tested in finished buildings with elevators unless it is for maintenance. But most of the time it is on a construction site where there is no elevator.

So to save myself from running up and down the steps 100 times, I created this box. It is comprised of 4 resistors in series with taps between each resistor. Just remember that the measured resistances of the box will have to be added to the actual bus duct resistance.

AC Voltage Switch Box

Having a switch box that switches on and off 120VAC is extremely beneficial and has a thousand uses. Well, I am exaggerating a little bit. Here are a few uses:

Electrical operation of 480V or 208V circuit breakers:

Most low voltage breakers utilize AC control voltage. Using a switch box, you can connect it to the secondary disconnects and switch on and off motor charging voltage, trip coil voltage, or close coil voltage. When primary/secondary injecting breakers, it requires many operations and having a switch box can make you a little more efficient.

Voltage testing of Voltage Transformers:

You can connect your 120V source up to the primary of any control power transformer or potential transformer in order to verify the ratio is correct. Use care as you never want to energize the 120V side of a 13800:120 transformer. Always apply the voltage to the primary side (H1 – H2) to avoid any electrical shock injuries.

My setup has 3 rocker switches. 2 of the switches give me switched hot wires and the 3rd switch gives me a switched receptacle. Black/Green = Hots, White = Neutral

Voltage Manipulation Box

This box is was put together for a specific task. It consists of multiple 4:1 transformers, 10kohm 100W resistor, 1kohm 100W resistor, 100watt 25ohm potentiometer, 1000V Rectifier, 120V fans. Most people ask me, why don’t you just purchase a box that can do that stuff. The simple answer is, you just can’t. The ability to sell and market a box like this would be directed to a very small audience.

The cost is not practical for a person to buy and may or may not be practical for a company to buy. If I were to sell a copy of my box, it would be for $4000 – $5000. There is just too much labor and the cost of the components aren’t exactly the cheapest. The pictures that follow contain some progress pictures as well as finished products. There is also a short demonstration video of voltage output of the box.

Custom Test Box Image Gallery