www.shaneburrell.com Telecom – Electronics – HAM Radio – Test Equipment – Rescue


Making something better. Hacking Lawnmowers. Deck Shaft Disconnect.

Sometimes I get something I really like and discover a big flaw in it's design. In the following case, my nice shiney new riding mower deck shaft had just given way again.  I believe this was the third failure.

The pot metal frame and weak steel direct shaft was a problem and after spending several hundred dollars over the past few years I decided to do something about it.  Off to the big shop.  After some quick layout in Fusion 360 and a quick 3d print of the housing for test fit, I started work on the shaft while the mill was cutting the housing.  I've gotten 2 complete mowings now before fall and it works great.  I was pressed for time on this but I did manage to snap a few photos of the new shaft and threading.

I also had to slightly modify a new tool holder I purchased as the ways were too tight for my liking so that took a bit of time to finish up.  Now I have a nice shiney new dedicated HSS cut off holder and a mower that won't fail me.

As a benefit the deck has never ran smoother and of course within an hour of mowing I found a bend cable plow blade.  The new shaft disconnected like it should and no damage to the mower.





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GPSTM Nortel Trimble hack.

Background of the GPSTM Conversion

I have several Symmetricom time references all of which are large.  I really needed something compact for my newest bench area. I fumbled upon a Nortel card (GPSTM). It is basically a Trimble Thunderbolt. It has a few minor differences, utilizing the same software for configuration. It has a 10mhz output (SMB Connectors). I used a Symmetricom Distribution Amp to sync all my equipment on the bench (Signal Gen, HP 8935 Spectrum Analyzer, HP Frequency Counter). The only modification required is a 48V(24-48VDC) DC power supply. It is very straightforward to get one of these up and running as a repurposed GPSDO. It is small, compact, and won't break the bank. I completed this project for well under $200.  A photo of the DC connection is below and a video as well.


Power Supply Modification

Nortel GPSTM Hack DC connection.

Nortel GPSTM DC Connection point.

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GPS DO Nortel Unit

I've added another GPSDO to my bench.  This is a Nortel unit.  Its fairly straightforward as its a Thunderbolt device.  Requires 48VDC power.

IMG_0666 IMG_0665




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Pulse Counters – The Kenwood TM-D710A keyboard hack.

I've got a ton of emails about the adapter for the Kenwood TM-D710A. The microphone on this unit uses a digital pulse counter based on 4017 logic IC's to determine, over a single wire, which key is pressed.  This same principle can be use in other projects to read a keypad, control LED's etc with on a pin or two from a microcontroller.  For reference below, are the articles on the TM-710A Adapter and associated projects.

http://www.shaneburrell.com/?p=688 - Keyboard Adapter itself - This board is line powered from the microphone cable. It effectively sits between the Kenwood radio unit and Microphone. It allows you to place a keyboard in between the two to allow functionality that Kenwood never intended per say.

Adapter Board PCB Prototype.

The theory of operation:  The microprocessor in the radio head unit sends pulses to the microphone.  On each pulse the line is pulled low which the microcontroller spies on via another pin attached to the pulse pin.  On a scope, it's very easy to see the line being pulled low depending on the keypress.  In hacking the pulses, its just a matter of seeing what key generates what pattern.   In the TM-D710A adapter I used a AVR to talk to the microphone and read a standard keyboard. The One Signal Wire board design above was used to Emulate the mic controlled by the AVR.

Pulse Counter in Action.

Below is a video some Arduino code I initially developed to scan the microphone patterns driving the Kenwood Mic from the AVR.  If you look at the scope this should give you a good idea how the pulse counter is working.

The TM-D710A keyboard hack was a really fun project and hit multiple stages of hack/design.  The 4017 counter is a pretty neat way of reading/controlling things using on 2 pins from a micro-controller.

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