Angelo Does Things

Breakout board for Anytone AT-D868UV external mic and speaker

2019-02-01T00:44:11-08:00

In the fall of 2018 I got a DMR radio, the Anytone AT-D868UV, for amateur radio use. Although it’s a rugged handheld radio, my primary use is at my desk in the home office.

For this use case, a separate microphone is handy to avoid needing to hold the radio or press the less-than-ergonomic PTT button. There are plenty of speaker-mics and headsets available for the Kenwood type connecton on the radio, but I wasn’t really interested in that. I have a good Elecraft MH3 microphone and plenty of headphones and speakers around the house. I didn’t want to spend the money on new hardware when I had perfectly good items already. When traveling, I’d also like to share one mic and speaker set with my other radios.

So I decided that I needed to find a way to make my microphone and an existing speaker place nice.

Step 1: Build a prototype

With a bit of research about the radio and mic connections, I was able to cobble together a circuit to connect them all together. This site was helpful for the Anytone connection, and this blog post was helpful for the microphone.

I didn’t have a Kenwood connector sitting around nor was I able to quickly find any, so I opted to get some 3.5mm and 2.5mm TRS audio plugs to do initial prototyping with. It was a bit janky, but it worked to prove the plan.

Janky "Kenwood" Connector

I eventually found this 2-pack of Kenwood style connection cables on Amazon. It turns out the keywords to find that were not the most obvious. Pro tip: search for “replacement cables” and “kenwood 2 pin”.

The finished prototype

As you can see, I also added a potentiometer to adjust the speaker volume. The radio has a loud internal speaker and it puts out just as much of a punch on the headphone line. By default the volume knob on the radio, when at the lowest setting, was still way too loud. You can adjust the maximum volume output in the radio settings, which adjusts all of the volume steps too, but I still wasn’t a fan of the granularity of the steps available using just the radio adjustments. The potentiometer helped immensely.

I used the prototype for a bit and decided it was a success. It was time to move on to the next step.

Step 2: Schematic

At this point, I decided that I wanted to make this a little more lasting than just the breadboarded prototype. It had been quite a long time since I had designed a schematic and I had never laid out a PCB. What better time than the present to give it a go?

I fired up the free version of EAGLE and did my best to remember anything from the electronics class I had in college.

The schematic

It did take me a while to figure out the right way to load in the components I was thinking about using. My first pass used whatever generic componets I could find in the libraries that come with EAGLE. With some searching I found online sources for the components I was going to buy.

During schematic design I also decided to make the radio connection an RJ-45 connector instead of directly soldering the wires from the Kenwood connector to the board. I wanted this breakout to be somewhat portable and reusable. Having a long wire hanging out of it felt like an annoyance, especially if I wanted to ever adjust how I was connecting to the radio. I also thought that perhaps this setup could be useful for other radios (such as my Yaesu FT2DR) too with just a change of the radio plug.

Step 3: Board Layout

At this point I was totally and completely out of my knowledge area. Time to learn.

I dug around Digi-Key to find the parts I would use for this. I selected them based on cost and whether I could find layout, footprint, and 3D model files for the component. Most of the time Digi-Key product pages linked to those useful files, and if not I just looked for them on SnapEDA directly.

The Board

After much playing around, I found (what I thought) was a pretty tight board layout that packed all the parts together in a useful way.

Rendered PCBs

Step 4: PCBs

I ordered the PCBs from OSH Park. They had a good balance of cost, turn-around time, reputation, simplicity, and capabilities for what I needed. Being my first set of boards, ever, I wasn’t really picky.

PCBs!

Step 5: Assembly

A little solder and scotch was all that was needed to assemble this project. The right ratio of scotch to solder is important, otherwise the results could be quite painful.

Preparation for assembly

Assembled!

Once assembled, I plugged it all in and gave it a test run. I was able to key up and the radio began transmitting – but my voice wasn’t being transmitted. Well crap.

After staring at the board, the schematic, and my prototype I realized that I missed two connections on the prototype when I made the schematic. Turns out I had done such a good job neatly hiding some of the wiring under other components on the breadboard that I forgot they existed. Oops.

Bug fixes

The schematic (and board layout) missed the microphone ground connection. I had only grounded PTT (which is why I was able to key up). I also missed the speaker connection to link the left and right channels together to make a single mono output. It was a quick fix with some wire to bridge the terminals on the board.

Step 6: It’s alive!

So far, this little adapter is working well. No longer am I worried about yanking wires apart when using my radio.

Prototype and final product

The final setup

The End

It isn’t perfect, but it’s wonderfully usable. It was a relatively simple project to break in to creating a schematic, board layout, and getting a PCB made.

I was disappointed when it seemed like my options were to buy an off-the-shelf speaker-mic or headset. Separating the speaker and mic for desk-use feels a lot more natural – and now I can also connect the radio to an external antenna during use!

This implementation is pretty specific to the MH3 microphone, but the concept could be adapted to any number of other microphones and radios. I hope someone else finds inspiration or help to build their own homebrew radio project to solve a problem they’re having.

Update: April 24, 2019

For anyone wanting to build this yourself, here are links to OSH Park and Digi-Key to order your own parts. The PCB is an updated version with the fix mentioned above already included in the design.

Digi-Key Shopping Cart

Mustang: Rear Seatbelts

2013-07-28T08:00:00-07:00

In the 1960‘s seatbelt laws were a relatively new thing. Until the National Traffic Safety and Motor Vehicle Safety Act was passed in 1966 there was no federal safety standards on automobiles. The law requiring seatbelts in all seats came in to effect in 1968. Cars manufactured before then generally had seatbelts as optional accessories. The front ones usually came by default and the rear belts were special order.

In the case of my ‘65 Mustang the front seats both had lap belts and the rear seats had nothing. At some point, a previous owner installed a lap belt for one of the rear seats. I’ve replaced the existing seatbelt (which was the wrong color) and installed a seatbelt for the other seat.

That almost looks like it’s supposed to be there!

Hooray for slightly more safety! This won’t, sadly, make those rear seats any more comfortable.

First trip to the doctor

2013-07-24T08:00:00-07:00

Just got the Mustang back this week from the shop. It had been there for the past two weeks. While I had dropped it off for what I had thought was going to routine clutch and transmission work – it didn’t quite turn out exactly that way.

For the first few weeks I have had the car, I was driving it all the time. Way more than it had been driven in a very long time. It was also the first manual transmission car I had ever driven more than just down the street. I had assumed, apparently incorrectly, that my terrible progress of learning to drive a manual had accelerated the death of the clutch. Apparently, though, it wasn’t me. And I’m better at driving a manual than I thought.

The clutch plate had been installed backwards by a previous mechanic. Backwards. How do you even make that mistake?

That, then, severely screwed up the flywheel and the flywheel bolts. Oh yeah, and the transmission input seal got damaged, most likely from the screwed up clutch. Really, all in all, a solid fuck up by someone in the past. Thanks.

Second gear was also causing problems by popping out. A synchronizer gear was to blame and so the transmission, with all this mess, needed to be rebuilt. And so it was.

Lastly the shifter was tightened up and the bushings replaced. No more slopping shifting for this car!

That car is even more of a pleasure to drive now. No more slipping, stalling, jumping, and popping. Smooth sailing all around. Knowing a good mechanic is priceless – except for the parts and labor, of course.

Quadcopter

2013-07-14T08:00:00-07:00

Back in May I picked up an AeroQuad Typhoon quadcopter kit at Maker Faire. I have been interested in model airplanes and other model flying things since I was little. I frequently had a styrofoam or balsa wood glider to play with in the yard. Gliders are fun – but throwing and chasing it around the yard got old after a while.

My Dad and I also had a gas powered model airplane many years ago (probably a good 10-15 years) that we only got out to fly a few times. Due to the need for a runway and space to fly we ended up having to join the AMA and a local club. They had a field and people who could help with instruction so we could actually learn to fly the thing.

I think the downfall of that experiment was the overhead of not just being able to pick up and fly it. That was a weekend hobby that wouldn’t get “fun” until a decent amount of effort was put in.

Fast forward to today where everything in that old airplane is outdated and archaic. For me, the introduction of the quadcopter (and other multi-rotor flying things) changed my thoughts on trying again. Quadcopters are generally easier to control, more stable, and the software on them can act like training wheels, keeping it upright and in the air (unless configure the accelerometer wrong).

The first few flights behind the house ended in collisions with walls and other things. I discovered the Sunnyvale Baylands Park via BayRC and it has worked out well for flying. I got the hang of it pretty quickly – and am now able to zip around the park. We’ll see how long it lasts before the first big crash.

Rose the Mustang

2013-07-08T08:00:00-07:00

I recently acquired a ‘65 Mustang convertible so you’ll start seeing things about it appear here. I’ve failed a bit at keeping up with posts about the Beetle – but I’m going to give this another go.

The name “Rose” was the name the previous owner used for the car. I’ve decided to keep it for lack of any truly better ideas (and to not confuse the car too much).

The photo above is from one of my first trips with the car down Skyline Blvd on the San Francisco peninsula.

Defcon 20 Badge Pin Layout

2012-08-05T08:00:00-07:00

Last weekend I was in Las Vegas for Defcon 20. The badge for Defcon was electronic and included a fully hackable microprocessor, the Parallax Propeller. Towards the end of the convention they were selling extra badges – which I grabbed two spares to use as Propeller development boards.

So, to actually use the board I needed to figure out what the hell the unlabled connection points at the top of the badge were (all the I/O, etc was unlabled). I figured I’d publish the results so someone else won’t have to go through the same identification process.

VW Beetle Project Part 6

2011-11-09T08:00:00-08:00

Recently I decided to re-upholster the seats in the Bug. Thus far I’ve made it through the two front seats. It’s been about 16+ hours of labor so far.

The Parts

The process is basically:

Take out seat
Strip seats to frame
Make repairs to frame/spring

In this case I had to weld the backrest spring back together.

Put new cover on spring
Put new cushion on
Cover cushion with felt
Put cover on seat
Attach buttons on backrest

This was interesting because I didn’t have new buttons to attach. The original seats were red and the new seats would be black. I decided I’d keep a little bit of the old car in there by keeping the faded, red buttons on the black seats. It adds a bit of uniqueness to the car.

Put seat in car

The seat on the left is the re-upholstered passenger seat.

The full gallery of images is here.

VW Beetle Project Part 5

2011-09-25T08:00:00-07:00

I’ve accomplished a whole bunch of stuff over the past month on the Bug (but I haven’t had time to post about it).

Washed the car
Lubricated frontend
Checked master cylinder
Adjusted the brakes
Adjusted e-brake setting
Adjusted steering wheel alignment (hooray driving straight!)
Fixed the passenger defrost vent airflow adjustment dial
Passenger seatbelt was attached incorrectly, causing it to be twisted
Replaced the door window rubber seals
Replaced door seals
Replaced visor clips
Fought with bent hinges on the driver side door (door doesn’t close right)
Replaced trunk liner
Replaced door panel attachment clips
Replaced trunk wiring cover
Replaced trunk rubber seal
Replaced engine rubber seal
Attempted to adjust the camber of the front, passenger wheel

VW Beetle Project Part 4

2011-08-22T08:00:00-07:00

Today I finally solved the mystery of the gas fumes in the cabin. The gas smell seemed to be heavy in the trunk, where the gas tank sits. Looking around I realized a few things:

The gas cap washer was dried out and brittle
The gas tank fill lines looked original to the car
The defroster vent hoses were a mess
One of the fresh air hoses in the engine compartment had a hole in it

Any or all of these things could have been the cause so I just fixed it all.

Every time I open another box from Wolfsbürg West it’s like Christmas

After I removed the gas fill hoses

The replaced gas fill hoses

I vacuumed and cleaned up the rest of the trunk.

The engine compartment is starting to look (and run) a lot better now too.

VW Beetle Project Part 3

2011-08-11T08:00:00-07:00

Over the past weekend I dove in to the first of the maintenance on the Beetle.

Valve adjustment
Oil change
Spark plug gap adjustment
Adjust distributer points
Adjust idle

Took me most of the weekend to work through it all and get it to the point where I was happy with things. At the beginning of the weekend the car would idle incredibly rough, stutter on acceleration and generally be a bit sluggish. I attributed this to the car just being old. Boy was I wrong. By the end of the weekend I was zipping around the block and it felt like a whole new car.

In the days since the weekend I’ve continued to work on tuning the idle. I got a new Tach-Dwell Meter on Tuesday which enabled me to check the distributer points more precisely and also verify the correct idle speed (850 rpm). The idle is a bit finicky, but as of Wednesday night I think I’ve finally got it between 850-900 rpm and running smooth.

During the spark plug gapping we discovered that the cylinder #4 spark plug was threaded incorrectly at some point in the past and now sits at a nasty angle. It definitely still works but I have a feeling that cylinder isn’t working at 100%. I’ll be investigating solutions including inserts and possibly replacement of the cylinder head.

It’s amazing what little things can make a big difference in a car. Today most cars “just work” and computers control most of the functions. Being able to see how every little thing in a car works, though, means you have so much more appreciation for what it does and how it does it. I’m starting to get a good “feel” for the car and can tell when things are “off”.

Next up I’m hoping to replace some worn engine parts such as the spark plugs and air hoses. Then on to replacing some of the gas tank parts. Those hoses are pretty damn old (and leaking smell – but no gas yet).