A ** NEW ** Do-it-Yourself Turning Target System

by Edwin C. Hall (December 2004)



New individual turner

Background

I've spent some time redesigning my turning target mechanism to create a more compact, easier to construct and less expensive version.  The new design is basically the same in concept, but the circuit has changed slightly as well as the construction.  Part of the new design was to remove the original tripod which now allows the user to choose their own means of mounting, whether it is still a tripod or perhaps attachment to an existing support.  The unit is still powered by a 12 volt, 4 (or 5) AH, sealed lead acid rechargeable battery which will last for several hours of use, however this new design has reversed the polarity of the system as will be seen in the new circuit diagram further down the page.  The system draws its short bursts of current (up to ~4A) only during the actual turning phases, a minimal amount (<100mA - depends on the relay used) while faced and none during edge time.

The heart of the turning system is a windshield wiper motor.  The particular one used for this project is described as a 2000-2001 Saturn L motor.  Other types may work, but this one started turning up at surplus places for around twenty dollars.  This type of motor has good torque and an integral switching system which can be used to limit the travel in one direction.  Therefore, only one more switch is needed to limit it in the other direction.  I found that for this alternate direction I also needed to provide a stop due to the inertia of the motor (and target).  The integral limiter stops the motor by reversing the polarity of the windings, but I didn't want to get that detailed in my construction of the other limit point.  In the present design there is a relay which controls the direction of travel, the integral limiter for edge position, and the added switch and bump stop for the face position.  The target does have a "bobble" at the end of its swing, but it turns in a relatively quick fashion and the "bobble" ends pretty soon.  The turning time is well less than a second, but is dependent on the weight of the target or system of targets.

This target system was designed to be faced by a short circuit contact device such as a switch or relay and edged when the short is removed.  Such a signal is provided by my Rangebox, a command playback and switching controller powered by a 9-volt battery.

I have built several of these, and decided to place this information into the public domain so others can build them.  If I can provide a means for someone to afford a turning system, then I'm happy to have published this page.  If help or more information is needed, contact me (15 Lakeview Ave, Tupper Lake, NY 12986).

A list of materials I use is at the end along with some source information.  Many of the parts are common type items found at many hardware stores, but some are from other places.  For some of the "others," I've also provided part numbers.

Of course, no printed instructions can be free of a safety reminder these days.  Due to the inability of me to be by your side through this, you will need to assume all risk involved with the construction and/or use of this system.  This includes, but is not limited to, the use of all tools involved.  Additionally, this system has moving parts!  Be aware of the pinch points and swing position of the frame when using it.  The battery should only be connected while you are not within the reach of the turning parts.  Disconnect the battery at any time you are within the swing radius.

Updates

Feel free to provide feedback on how this project has worked.  I will try to change it if better parts appear or techniques evolve.  I have reviewed this document countless times, but there is no guarantee of accuracy.  If an error is found, I will attempt to immediately get the correction out.  Please feel free to send me comments.

Construction

In an attempt to avoid confusion, I will refer to the motor and housing in the following manner:

Orientation of the motor unit

Orient the motor assembly such that it is sitting in front of you with the shaft at the upper right.  This should place the motor horizontally to the lower left as in the picture.  Where the black motor cover meets the grey housing, two wires emerge and travel to the back of the connector on the bottom of the housing.  The mounting hole just above these wires will be referenced as #1.  Moving clockwise, the next mounting hole is #2 and the last one is #3.  The connections on the bottom of the unit will be referenced by the numbers given on the connector housing.  In case you get a motor which has different markings, this can be a key: A=53b, B=53a, C=53e, D=31b and E=53.  A-E will be from the left looking into the connector with it on the bottom and the shaft pointing upward.  The lever arm mounted on the shaft will be referred to as the arm.  This arm has a "hitch" type ball on the end.  Its orientation at this point will not be important.

Holes drilled in the washer and bracket will be numbered to match with the numbering of the motor housing holes to start out.  Subsequent holes made through the washer and bracket will be numbered as they are mentioned, as referenced in the pictures.

The new bracket and washer

Steps to Construction - Working With the Motor and Washer

Moving to the Bracket

Arm with modifications

Working with the Arm

Switch Placement

Some of the Wiring

New wiring diagram

Note: The shield of the jack must not be attached to ground in any way. Either use a plastic jack with isolated mounting like the one in the parts list (preferred) or use the ring and tip of a stereo type jack AND plug. Even with a stereo jack, if the shield is grounded and a monaural plug is inserted, it will cause a short of the shield to ground. This will cause an overcurrent!





Some Testing and Setting of the Stop Position

Note: This last step is very important!

Back to the Arm

Connecting Up the Battery

Building the Target Frame

Making a Connecting Cable

Final Testing

The new system close up

Suggested Tools and Materials List:

Note: Several drill bits will be determined by what your tap suggests as the starting hole.

Parts List: (Source and P/N of part)

Note: Some of the parts I used for this project came from All Electronics.  I am in no way affiliated with them other than being a customer.  There are several other sources for many of these parts or similar.  I provided this list with All Electronic part numbers solely for your information.  Parts availability changes frequently, so you may need to research a part to find a similar one.  For all the parts other than the isolated (plastic housing) 1/4" jack, many other styles of part can be used.  Feel free to use alternate vendors.  For items without part numbers, these should be readily available from hardware stores.