Saturday, 26 September 2015

Yaesu FT-847 DRM

This post has been reproduced from my old web pages. There has been some call for the 12KHz mod info since I took my old site down.

I've been promising myself that I'd convert my FT-847 to DRM use for a few years but with DRM broadcasts here in the US only being available in the early evening when I'm tied up with family matters there seemed to be little point.

However, RCI recently announced that they would be transmitting programmes throughout the month of December (2006) from 1500UTC until their normal shutdown time of 0000UTC; a whopping nine hours of programming every day! Where's my soldering iron?

A while back I ordered a couple of 455KHz-12KHz down converters from I5XWW with a view to doing this job. These converters use a freely available design found in a number of places on the Net. Frankly for the amount I5XWW charges for these pre-built boards it's not worth the hassle of building a convertor on a project board. I paid $15 each for them!

OK, lets get down to it. On a clean work surface (not like mine) remove both the covers from your FT-847 and place it upside down on the bench with the sockets facing you. If like mine your's is a stock radio then you will have a vacant space on the upper left quadrant. This space is earmarked for the installation of the optional CW filter. This is where we are going to install the board.

Next make sure you have the following items;

RCA phono socket
12" hookup wire
24" RG174 coax
22pF capacitor (other values may work)

As you can see from the picture this mod is very simple and there is plenty of working space inside the 847.

Let's start by mounting the convertor. I used a strip of double sided tape.

Now let's tap the 455KHz IF. Locate the 8 pin IC just below the vertical SSB filter. Solder one leg of your 22pF cap to pin 2 of this IC. Pin 2 is the second pin from the right on the top row in this orientation.

Next prepare a length of coax. Connect the center to the open end of the 22pF cap and the shield to pin 4 of the chip (top row, left most pin).

Be sure to check your work for solder splashes and shorts etc. Also make certain that the new parts will not come adrift and cause damage.

Connect the other end of this coax to the 455KHz input of the convertor. In my case this was the top left 2 pins.

Take the hookup wire and attach one end to the screw terminal with the red wire on the right of the board. I used the one above the fuse. Connect the other end to the converter's power connection.

Now comes the hard bit. We have to find a space to mount the connector. As you'll see there isn't much room on the back panel and so I drilled a small hole and passed the coax cable through thus allowing the connector to hang out of the back. Connect the RCA socket to the end of the cable that hangs out of the radio. Connect the other end to the convertor output pins.

That's pretty much it. Before putting your radio back together again, fire it up to check everything is OK. You'll also have to set the output level so that there's enough to drive your sound card.

Below are pictures of the work and also of the relevant DReaM software screens.

Friday, 20 March 2015

Yet Another Reflow Oven

There's something very satisfying about making your own stuff. As you'll have seen by my previous posts I design a lot of my own circuits. To this end I've built a Surface Mount Device Reflow Oven.

I was inspired by this youtube video. The thing that impressed me about it was the price; small reflow ovens can cost upwards of US$500. The toaster oven used in the video is still (March 2015) on sale at Walmart for less than US$20. But like most things based on an Arduino, not only does it require an Arduino board at some US$30+ but it needs a shield to connect all the temperature sensing and heating elements etc at a further US$35. So that would make the total something like US$100 or more. Still not ideal.

So thinking that I could do better I set about designing my own "embedded Arduino" based controller. It would have all the same facilities as the one in the video but everything would be contained on a single PCB where possible.

This is what I came up with. The board above contains an AC power supply, LCD interface, temperature sensor, interface buttons, buzzer, FTDI serial interface and of course, an Arduino.

So then all I needed was firmware for the Arduino. There was no point trying to write my own. It's not as if I've had an original idea here. Casting about the 'net I came across this website where IanJ describes his journey creating a similar oven. I downloaded Ian's code and set about adapting it to my board. It was quite easy really. I simply needed to move some pin assignments around and change some of the outputs from low to high etc. My modified version of the code can be found below. It still requires the library from Ian's website (don't forget to modify the library for Arduino IDE 1.x+).

My design differs from Ian's slightly in that I use a PNP transistor to toggle the relay that in turn powers the heater elements. I've also used the analog pins in digital mode so that I could make the board layout easier for a milling machine or home brewers doing single sided boards and likewise I have not used the traditional LCD pins but rather moved them  to other pins for the same reasons. Other than that we've come up with more-or-less the same design.

If you want a copy of the board you can buy it from Oshpark. Be aware that there is a minor error on the PCB. The "fix" is to raise pin 21 of the Arduino such that it does not connect with the IC socket. I had inadvertently connected that pin to ground when it should have been either pulled up or left floating.

Parts list and costs ...

"Rival" brand toaster oven - $18.47 @ Walmart
Solid state relay - $1 @ ebay
Welding blanket - $18 @ ebay
"K" type thermocouple (minimum 350c) - $1 @ ebay
PCB - $10 @ Oshpark
Arduino - $3 @
LCD - $2 @ ebay
R's, C's etc, - $3 @ junque box
AD595 temperature sensor - $3 @ ebay
Total = $60 or thereabouts

 The usual files in Eagle format and GCode for your CNC mill ...


Saturday, 7 March 2015

Ebay 3020 desktop CNC router

I bought one of these 3 axis CNC routers via ebay. My goal is to make my own PCB's with it. Well, yeah; that's my goal. But in the 9 months I've owned it I've not yet been able to get a satisfactory piece of work from it. As is usual with most things from China via Ebay, the documentation was non-existant. I got most of my information from other frustrated owners on various mailing lists and message boards. 

Sales picture from ebay
My first issue was that it needed a PC with a parallel port. Having a "legacy free" PC was going to cause problems. As it turned out that problem solved itself. I'm a Linux user. Having done some research on how to use this thing with Linux I discovered that there is an entire Linux CNC project dedicated to these sorts of machines. Because the timing demands of the router are pretty specific Linux CNC requires its own PC hardware. I was able to find a suitable PC in the junk pile that would run the router "properly".

I say "properly" as the supplied controller (the thing in the black box) was pretty lacking in its features. Not only that but when I tried to use the demonstration CNC projects supplied with the Linux software the router became intermitant. Investigation of the controller box revealed that the enclosed circuit board was not grounded at all!! It relied on a single screw thread poking through a mounting hole. Unfortunately the screw head was covered in paint. A wire brush fixed the paint problem and a few other ground cables added here and there brought the lighted power switch into operation. Great, now it would route the demonstration piece.

Rear panel of the controller
Take a look at the back of the controller. Can you see that blanking cover? What is that for? Well, closer examination of the circuit board revealed 4 axis abilities as well as limit switches and a few other features not normally available by default. Do you see that coaxial connector next to the parallel port (click the picture to enlarge it)? At first I thought it was to supply DC power instead of using the built in mains PSU. Good job I didn't try connecting anything to it as it turned out to be the Z axis probe input (used to detect if the router bit has contacted the work piece).

Inside of the controller. Note linear PSU and 2 control boards

Spindle control not connected to anything
Whilst poking around the board I noted a few other things that were useful. As supplied the controller requires manual control of the motor spindle that drives the actual router bit itself. One presses a switch to start the motor and then winds a knob to adjust the bit rotation speed. What a load of crap!!. Why can't the PC turn the spindle off and on and adjust the speed as needed? Turns out that the PC can do these things if only the jumpers on the circuit board were set correctly!! The vacant white connector at the top of the right hand picture controls the bit speed.  Control of the bit spindle was achieved by cross connecting the PWM-OUT on the below board to this connector. The picture also shows the bad grounding issues I dealt with. Here we see that the mounting holes are painted over thus insulating the ground path.

Limit and bit spindle outputs not connected to anything
That brings us back to the limit switches. There's a header on the board that allows for limits on 3 axis. I found a 4 pin CB microphone connectors in my junk box and wired it into the limit header on the circuit board. I still need to install the actual switches on the router itself as they are missing too but unlike the controller circuit board there is no provision for adding these. I bought a few of these switches via ebay and I think I'll try and make a mounting bracket with my new 3D printer. Alternatively I could make the brackets with the router itself?

Limit switches brought to the back of the control box

A-axis output just below the left white connector
So now we have to connect the router to the PC by way of the printer port. My chosen software needed me to create a machine profile so that it would know how to drive the router. This meant having to map the pin functions from the controller to the PC. The below is what I came up with.

Since starting on this journey I have run across some other websites that have also found the same issues as I have. This one is by far the most detailed.

Friday, 6 March 2015

Build your own "Internet"

By now you've probably seen see this sketch from the TV show "The IT Crowd"?  Jen is fooled into believing that a small black box with a flashing light on the top is in fact what the Internet looks like.

I gave a talk recently at a gathering of Shortwave radio listeners. I decided that I would demonstrate the "Internet" as part of my talk so I set about building one of my own. It's incredibly simple and requires just a few $$ of parts and a black plastic box.
I got the above circuit from the real Internet. Note that the circuit has 2 LED's. To make a clone of the original "Internet" one needs only to use a single LED however, the two LED's gave me an idea ..... build a second device which would use both LED's into a smaller box and call it "The Internet V2.0". After all, Moore's Law dictates that everything becomes smaller, cheaper and has more facilities.

My boxes had a 9V battery for power and the circuit was stuck onto the inside of the lid with double sided tape.

It you want to make one of your own you can buy a board from Oshpark

As usual, here are the files in Eagle format along with GCode for your CNC mill ...

555 Internet Flasher.pdf
555 Internet Flasher.sch
555 Internet Flasher.brd
555 Internet

Wednesday, 25 February 2015

Give your telescope some teeth

I recently bought a new mount for my Celestron C6 telescope. I am now the proud owner of a Celestron Advanced VX mount. I've not had it outside yet (its still a balmy -10C outside!) but I'm very pleased with its stability and ease of use. I have it set up in my basement and have been getting all the remote control software organised for it so that I can try my hand at some astrophotography when the weather breaks.

As you can see it has a hand controller that will allow me to manually drive the mount to any of over 10000 objects. But for taking pictures I need to have computer control. Luckily this mount comes with that already enabled by way of a RS232 cable that plugs into the bottom of the handset. Only 2 problems here; 1) I have no serial port on my laptop, 2) I must be "tethered" to the mount. I dunno about you but I'd rather have the least amount of cables dragging around my equipment especially when its dark and I can't see them. So wireless is my goal.

One can buy a WiFi enabled remote control device that plugs into the mount but its $100 and as it's WiFi it'll quickly kill the batteries of any mobile device I use with it in place of the PC. Bluetooth is the solution that springs to mind. It has a serial port emulation ability and uses much less power than WiFi.

Other owners have had this idea too. I've seen some interesting attempts to add Bluetooth abilities to this mount. Most of them are a lash up of common off-the-shelf parts and added wires. This solution costs over $130. So whilst sitting on the pot the other day (I do my best thinking in there) I had an idea , "why not connect something directly to the Aux connector on the mount?". Looking at the wiring diagram for the connector we can see that there is 12V of power and 5V TTL serial data available. Indeed, this is what the WiFi adapter uses for it's power and comms as does the GPS receiver addon.

This is what I came up with. One adds a 6 pin telephone cord between the adapter and the Aux socket at which point it'll spring to life. The missing part on the board rendering above is an HC-06 Bluetooth interface. The rest of the stuff is power conversion and such like. Following the "howto" I installed the relevant software and was able to control my mount from my PC. I've also tried it with Sky Safari on my Android tablet too. Works perfectly! I can even remove the hand controller from the mount which will help when up at the club site preventing visitors from playing with my scope when I'm not looking.

False Teeth under test
I'm calling the project "False Teeth" as the device is not blessed by Celestron.

Files in Eagle format ...
False Teeth.pdf
False Teeth.sch
False Teeth.brd