A2Z Tech WA2IVD Mini Bar Crowbar Circuit Full Kit Instruction Manual

: June 17, 2024
: A2Z Tech

Table of Contents

A2Z Tech WA2IVD Mini Bar Crowbar Circuit Full Kit Instruction Manual
Thank you for purchasing the MiniBar Full Kit!
Introduction
Parts List
Circuit Details
PC Board Front side Copper & Silkscreen
Assembly instructions
Solder the fuse holder.
Using the MiniBar
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A2Z Tech WA2IVD Mini Bar Crowbar Circuit Full Kit Instruction Manual

Thank you for purchasing the MiniBar Full Kit!

Introduction

The MiniBar crow-bar circuit is designed to protect electronic equipment from damage because of over-voltage in the event of a power supply failure. It isdesigned for equipment that operates nominally at 13.8 Volts DC. It is designed to trip and blow the on-board fuse at approximately 15 Volts DC. This is well withinthe safe operating range for most radio equipment and is still above the maximum output for regulated power supplies and automotive charging systems.
Revision C of the circuit includes an additional filter capacitor on the SCR gate to prevent inadvertent tripping from voltage spikes that may occur if it is connected to a live power source, such as a battery and charger combination.

Thank you for purchasing the MiniBar crowbar circuit kit!

Parts List

Circuit Details

The positive load current goes through the fuse and solid copper planes on the front side of the board. Negative load current goes through a solid copper plane on the back side of the board.
C1A in the REV B version provides additional protection from noise and short voltage spikes.

PC Board Front side Copper & Silkscreen

PC Board Back side Copper (viewed from front)

Assembly instructions

Important: You will be soldering large terminals to solid copper planes. You will need to use at least a 50-75 watt soldering iron or a temperature controlled soldering station. You should be using a large chisel tip.
If you have a soldering station, set the temperature to the higher end of what you normally solder at.
It is counterintuitive, but the higher temperature actually helps to minimize the chance of damaging the PC board by heating theterminals and PC board up quickly to melt the solder faster.
[ ] Insert one of the Anderson PowerPole 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 butterfly 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 into the PC Board. The center plastic 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 bottom 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 bottom of the board and the bottom 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 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 15.0 volts, nominally. Its primary purpose is to prevent the radio or other electronic load from ever seeing excessive voltage. The actual trip voltage may range from 14.6 to 15.4 volts. When the fuse has been blown, the red Fault LED next to the fuseholder will illuminate. If no load is connected, the red Fault LED and green output LED will both light.
NOTE: REV C of the MiniBar includes capacitor C2 in the SCR gate circuit to prevent trips from voltage spikes when connecting to a live DC power source. However, it is still good practice to turn power off whenever possible before connecting 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 station accessory, or some type of power distribution box.
A fuse is not included with the MiniBar. You must select a fuse rating appropriate to the load(s) you are powering.
The maximum allowable fuse is 30 Amps.
NOTE: The MiniBar PC Board can handle approximately 15 Amps continuous
current. For higher currents, up to 30 amps, you must operate at 50% duty cycle or less and no more than 30 seconds continuous at 30 amps. This should be
adequate for operating SSB, Data, or CW with typical 100W radios.
IMPORANT : Your power source must be able to deliver at least 2X more current than whatever fuse rating you choose. If your power source delivers less current, the fuse might not trip reliably.