Mr. BulletFeeder Motor and Circuit Testing

[JigSaw]

Hello all,
I started loading some 9mm for a customer this morning and got about 300rds out when my Mr. Bulletfeeder quit working. It stopped dead in its tracks without any warning. Where I have my loading bench setup happens to be next to where i store my cameras and tools so i decided to do a "How to"

I don't intend to be showing the correct practices, or proper usage of tools or even a camera, so please hold criticism on that front. What I do intend to do is show how to take some readings with a simple Volt and Ohm meter. (Mine isn't simple but the same test can be done w/ a cheap radio shak model).

While you can take the measurements of the circuit in any order you want, I will be describing the measurements in the same order as the video i took and edited. The diagnostic process could have easily taken just a few steps, and have been performed w/ all of the parts installed on the Bulletfeeder assembly. I removed everything and took extra steps to assist in helping you understand the "How" and "Why." I hope this post and video (9 minutes long) will help someone that doesn't understand electrical testing, get a handle on verifying which part of their device is causing them an issue.

The practices of Ohm testing and Voltage Drop measurements can be applied to just about any simple circuit. As long as there are no Data or Logic circuits involved, testing a system in the same manner as I have tested the Bulletfeeder Motor circuit should work out great for you.

I'll do my best to keep the pictures in testing order.



If you have a look at the Schematic I drew of the circuit you will see it is very simple. Power comes in from the plug to the Positive side of the motor. The ground side of the motor is then attached to the coil of wire that runs to the switch mounted on the bullet tube. The switch acts as the control device and opens the contacts when a bullet is present and holding the lever out. Once there is no bullet pushing on the lever, the switch closes and allows the Ground side of the motor to be connected to the Ground side of the power supply, completing the circuit and causing the motor to rotate.


1st. I set the meter to Volts and check the Power Supply for voltage. You can do this at the barrel plug or at the terminals inside the housing as I have done in the Video.


2nd. I check for supply voltage through the switch assembly. This effectively checks for voltage though everything BUT the motor.


3rd. I plug in the motor and do a Voltage Drop across the motor with the circuit under load. Since the only load in the circuit is the motor, we should see ALL of the source voltage being dropped across the motor. If we see a reading of significantly less than source voltage (more than a .5volt difference) then we have another load (source of resistance) in our circuit.


4th. Given our reading I opt to replace the motor with another load in order to do a Voltage Drop across a known good part. It is common when testing automotive circuits to add a test light into the circuit and wire it so that the Light is connected to the battery on one side of the circuit, and to the entire expanse of the opposite side of the circuit that a fault is believed to be in. After checking each side, Power and Ground, of a suspect circuit in that manner, you can then condemn the Part that the circuit controls or continue component testing if need be.

5th. In the video I use the variable output of the motor controller to simulate a bad reading during a voltage drop test. We see 10.66 volts on a circuit that should be 12.28 volts. If you see a reading like this you know that somewhere else in the circuit you have resistance that is consuming that lost voltage.

6th I demonstrate the proper way to perform a voltage drop on the remaining portions of the circuit.

Finally we do a little Ohm testing of some parts and circuits. An Ohm meter reading can be very valuable, but don't allow it to confuse you. Just because a circuit has an Ohm reading that is acceptable, doesn't mean it is capable of carrying a load. If a wire were cut, pinched, or damaged in some way yet a single strand was left connected it would likely pass an Ohms test. If you take that same wire and load it in a circuit, it will quickly fail a Voltage Drop test and consume part of your Voltage that you intend for your load (motor in our case)

The Video:

I hope this helps someone understand the circuit and how to test it if you have an issue. Feel free to PM if you have any questions or advice how to make this "How To" better for future readers.

Thank You,

Matt R. Edited December 22, 2014 by JigSaw

[Sarge]

OK........So did you find the problem? Typically with the MBF it's a fuse that is hidden up under the housing.

[JigSaw]

Bad Motor.

You will notice by the video that the Buzzer (motor replacement) makes noise and all of the circuit tests good

[Sarge]

I have much too short of an attention span. I barely made it through the post let alone watch the video. Get a hold of Saul and see what he can do for you.