A2Z Tech Mini-Bar 15-16 Crowbar Circuit Full kit Instruction Manual

: June 1, 2024
: A2Z Tech

Table of Contents

IntroducƟon
Parts List
Circuit Details
Assembly instrucƟons
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A2Z Tech Mini-Bar 15-16 Crowbar Circuit Full kit Instruction Manual

Thank you for purchasing the MiniBar 15-16 Full Kit!

IntroducƟon

The MiniBar 15-16 crow-bar circuit is designed to protect electronic equipment from damage because of over-voltage in the event of a power supply failure. It is designed for radio and electronic equipment that operates nominally at 13.8 Volts DC. The MiniBar 15-16 can be set to trip at 15 volts or 16 volts. The 15 volt seƫng is best when operaƟng directly from a 13.8 volt power supply and provides the highest level of protecƟon for electronic equipment.

The 16 volt seƫng can be used when operaƟng from a vehicle 12 volt charging system or from lithium ion baƩeries while connected to solar or other charging equipment. Some lithium baƩery charging systems and automoƟve charging systems can operate very close to 15 volts under certain condiƟons. The 16 volt trip seƫng provides addiƟonal margin against false trips while sƟll providing overvoltage protecƟon for sensiƟve loads.

The MiniBar 15-16 includes the addiƟonal filtering to filter noise spikes that might trip the crowbar if it is plugged directly into a live power source.

Thank you for purchasing the MiniBar 15-16 crowbar circuit kit!

Parts List

Circuit Details

The posiƟve load current goes through the fuse and solid copper planes on the front side of the board. NegaƟve load current goes through a solid copper plane on the back side of the board.

PC Board Front side Copper & Silkscreen

PC Board Back side Copper (viewed from front)

Assembly instrucƟons

Important: You will be soldering large terminals to solid copper planes. You will need to use at least a 50-75 waƩ soldering iron or a temperature controlled soldering staƟon. You should be using a large chisel Ɵp.
If you have a soldering staƟon, set the temperature to at least 680F (360C).
It is counterintuiƟve, but the higher temperature actually helps to minimize the chance of damaging the PC board by heaƟng the terminals and PC board up quickly to melt the solder faster.

[ ] Install the 3 pin header (J1) on the board

Hold the header in place while soldering ONLY ONE Pin on the back side of the board.If you don’t have a Helping Hands or similar device, you can hold the header in place by placing the board upside down on your workbench.

[ ] Confirm that the header is verƟcal and flush to the board. You can re-melt the solder on the one pin to reposiƟon the header. Once the header is properly placed, then solder the remaining 2 pins.

[ ] Install the jumper to select desired trip voltage.
Pin 1 is closest to J1 label on PC board.
– Jumper Pins 1-2 for 15V trip
– Jumper Pins 2-3 for 16V trip

15V trip is shown

[ ] Insert one of the Anderson Power Pole connectors into the Input or Output slots on the PC Board.
The back side of the connector (closest to the solder terminals) must be held flush to the board while it is being soldered.
If you don’t have a small vise or other clamp, a large buƩerfly clip (found in office supply stores) can be used as a clamp to hold the connector in place while it is soldered.

Solder the connector in place
[ ] Insert the other Anderson PowerPole connector into Board.
Be sure the connector is flush to the board and solder it in place. [ ] Insert the fuse holder (F1) into the PC Board. The center plasƟc post on the fuse holder will snap into the center hole on the board and hold it in place. Solder the fuse holder. [ ] Assemble the top and boƩom acrylic plates using the provided screws, nuts and spacers.

The top acrylic plate is pre-cut for the fuse holder.

The smaller (1/8”) spacers go between the boƩom of the board and the boƩom acrylic plate. The larger (3/8”) spacers go between the board and the top acrylic plate.

Using the MiniBar

When power is available at the output connector, a green LED (D4) next to the output connector will be lit.

The MiniBar monitors the voltage from the power source. It will trip and put a short circuit across the input fuse if the power source voltage exceeds 15 or 16 volts, depending on the selecƟon. Its primary purpose is to prevent the radio or other electronic load from ever seeing excessive voltage.

The actual trip voltage will vary based on operaƟng temperature and component tolerances.

15V seƫng – 14.6 to 15.4 volts
16V seƫng – 15.6 to 16.4 volts

When the fuse has been blown, the red Fault LED (D1) next to the fuseholder will illuminate. If no load or a very small load is connected, the red Fault LED and green output LED will both light.

Capacitor C2 in the SCR gate circuit helps prevent false trips from voltage spikes when connecƟng to a live DC power source. However, it is sƟll good pracƟce to turn power off whenever possible before connecƟng power sources, loads, or other equipment.

Connect the IN side of the MiniBar to your power source. Connect the OUT connector of the MiniBar to your load.

This might be a radio, a staƟon accessory, or some type of power distribuƟon box.

A fuse is not included with the MiniBar. You must select a fuse raƟng appropriate to the load(s) you are powering.
The maximum allowable fuse is 30 Amps.

IMPORTANT: Always use high-quality brand name fuses, such as EatonBussmann®, LiƩelfuse®, or similar.

MiniBar 15-16 Full Kit Assembly Manual 10
NOTE: The MiniBar 15-16 PC Board can

NOTE: The MiniBar 15-16 PC Board can handle approximately 15 Amps conƟnuous current. For higher currents, up to 30 amps, you must operate at 50% duty cycle or less and no more than 30 seconds conƟnuous at 30 amps. This should be adequate for operaƟng SSB, FT8, or CW with typical 100W radios.

For data modes with long transmission Ɵmes such as SSTV or RTTY with lengthy text, you will need to reduce output power to approximately 50 waƩs or less to avoid overheaƟng the MiniBar.

IMPORANT: Your power source must be able to deliver at least 2X more current than whatever fuse raƟng you choose. If your power source delivers less current, the fuse might not trip reliably.
If your power source cannot deliver sufficient current to blow the fuse, the MiniBar can overheat and will be damaged.