Designing antenna arrays with adjustable beam width, azimuth, and elevation angles.
by Jim Lux, w6rmk
by Jim Lux, w6rmk
A simple antenna tuner made from switches. How to determine the “best” transmission line lengths for multi-band center fed wire dipoles.
by Cecil Moore, W5DXP
And other ways to remotely control existing dials.
Suggestions from robotshop.com: http://www.robotshop.com/forum/post-p101569
from p3america: http://www.p3america.com/motorized_potentiometers_text.htm?gclid=CJSetfSYusUCFdOQHwodPEUAaw
From Online Controls: http://www.onlinecontrols.com/mpots.htm
Sparkfun motorized fader (like the kind used in DAW control surfaces) https://www.sparkfun.com/products/10976
from electronics stack exchange: http://electronics.stackexchange.com/questions/60272/servo-controlled-potentiometer-using-rotary-position-sensor
The Potentiometer Handbook by Carl David Todd: https://www.bourns.com/pdfs/onlinepotentiometerhandbook.pdf
Google search: servo to turn a knob
Shower temperature control from SmithyTech: http://smithytech.com/?p=5
Arduino HVAC Servo Thermostat/Controller by tikka308: http://www.instructables.com/id/Arduino-HVAC-Servo-ThermostatController/
What kind of motor would I need to turn this central heating valve? http://electronics.stackexchange.com/questions/97269/what-kind-of-motor-would-i-need-to-turn-this-central-heating-valve – observations about the difficulty of using robots to turn knobs
Sous vide cooker with feedback control: http://www.nerdkits.com/videos/sous-vide/
Homemade Electric Telescope Focuser: http://emediadesigns.com/focuser/
Use your Raspberry Pi to move parts of a robot or control anything that can rotate – by Rob Zwetsloot http://www.linuxuser.co.uk/tutorials/control-servos-with-a-raspberry-pi
Resistance and capacitance in an AM radio.
A first test to find out if its practical to ‘piggyback’ external controls on to an existing radio. The reason for doing this is to leave an original radio intact by clipping the remote components to the leads of the existing controls.
For example a varactor would be connected in parallel to the variable capacitor already in the circuit. The existing capacitor would be set low. The capacitance of the varactor would then be added to the total, using the formula for parallel capacitors.
For potentiometers, its not as easy because parallel resistors are divided:
Formula: Rtotal = R1×R2/(R1+R2)
For example if R1 is 10K, R2 would need to be 100K to get a total resistance of 9K. To get 99% of the existing resistance, the piggyback resistor needs to be 100 times the value of the existing resistor. 1 MegOhm if matched with 10K.
What happens when the radio is not being controlled remotely?
Conversely, how should the physical controls on the radio be set when operating remotely?
SPST switches can be considered as a form of potentiometer with infinite resistance. A piggybacked switch will only work if the existing switch is in the ‘off’ position. And vice-versa.
Double-Throw and Rotary switches present more difficulties as multiple states are maintained by the same device.
I don’t think multiple throw switches can be piggybacked. Two possible solutions:
I piggybacked a tuning capacitor from an AM radio onto the tuning capacitor of a vintage Radio Shack Globe Patrol (regenerative receiver).
Audio/video synthesizer with hacked VGA cables.
By James H. Connolly
http://jameshconnolly.com/rgb-vga-volt
A better tutorial (with warnings) on building the cables, at CrackedRayTube, also by James Connolly with Kyle Evans: http://crackedraytube.com/pdfs/hacking_a_vga_monitor.pdf
Max patch for controlling the system: http://jameshconnolly.com/rgbvgavolt/RGB.VGA.VOLT.zip
A new memristor-based device could be used to build brainlike systems and base-10 computers.
At Trinity College, Dublin. Article by Alexander Hellemans at spectrum.ieee.org
http://spectrum.ieee.org/semiconductors/memory/sixstate-memristor-opens-door-to-weird-computing
Scanned PDF files of classic electronics magazines.
http://www.americanradiohistory.com/Popular-Electronics-Guide.htm
Lots of information in a few pixels.
Computer displays have evolved to high resolutions. What about the other direction? This experiment is a display interface using a grid of LED’s. Essentially, very large pixels.
LED’s communicate information using
With just a few LED’s its easy to display a clear message. A large matrix of LEDS can get confusing. Here are a few suggestions:
An effective but inefficient signaling method.
Resistors use a numeric color code.
Find the value of any resistor by looking at the first four 4 color bands. Colors represent base 10 exponential notation.
An abacus uses 5 or 10 beads for each digit. Faster than decoding a resistor and works with one color – but takes up more space.
Segmented level meters convey information using a line of pixels:
Represents digits using binary coded decimal notation.
This grid design was used for the visual interface of a shortwave radio:
And an etch-a-sketch:
https://github.com/tkzic/max-projects
folder: LED-display/rx-320/
files:
There are 2 large toggles – one for etch-a-sketch, and another for the radio simulator. Try one, then toggle it off before trying another one. If you forget – just restart the patch.
The number box near the top can be used to expand or contract the display size (while it is active) The default size is 17.
The same patch generated both video examples above. It uses javascript to make a two dimensional array of Max led objects. Each object is addressable by its position in the array. Here’s the code to make the objects:
// // makecells - create matrix of led objects // function makecells( x, y, color ) { var p; // this patcher var tmpstr; var objname; post( "makecells: ", x, y, color ); post( ); p = this.patcher; // make cells for( i = 0; i < x; i++ ) { for(j = 0; j < y; j++ ) { cell[i][j] = p.newdefault(xorigin + (i * cellspace), yorigin + (j * cellspace), "led" ); // create leds if(color != 9 ) { cell[i][j].hidden = 0; cell[i][j].message( "pict", color ); } else { cell[i][j].hidden = 1; } cell[i][j].varname = "led" + i + "x" + j; // assigns name for future use } } }
Although each LED in a grid is addressable, its easier to group sections of the grid into blobs. Each blob is a unit that displays data, like a number for example. There are several types of blobs:
Here are the properties of a blob:
// blob data structure // // x, y upper left // lengthx, lengthy, // // orientation: 0 = horizontal, 1 = vertical // step 1 = downward or rightward, -1 = upward or leftward (this defines the corner of origin too) // // data lorange, hirange // scale: 0 = no, 1 = yes // // blobtype: 0 = generic decimal, 1 = spare, 2 = pushbutton flash, 3 = radiobutton, // color code 0-9 // contrast color 0-9 // // signed ( 0 = no, 1 = yes) // booooooooooooooolean // colorshift ( 0 = normal , 1 = use different colors every 3 digits, like comma separators (frequency display) // // blink (milliseconds duration for pushbutton flash type only (led blinktime ) // // radio number // name // value // //
Lets look at examples of various ways to display data – as used in the shortwave radio video above.
Here are 3 blobs that represent numbers in three different ways.
The far left column and the bottom row are key graphics. They give a frame of reference for the data.
Moving from left to right…
The LED’s far left column, are a graphic key, starting with red on the bottom, represent the numbers 1-9
The next blue column is just a divider
The 3rd column of white dots is the signal strength data ranging from the 0-9. The current value is ‘4’, represented by a column of 4 dots.
The next nine columns (4-12) represent the frequency in Hz. ranging from 0-999,999,999. The data is in groups of three (as you can see by looking at the graphical key in the bottom row). The number currently displayed is: 4,999,991.
Negative frequencies are displayed by shifting the colors to values that don’t match the key graphic.
The last column is a radio button with 4 possible values and is currently set to ‘3’
The bottom row is a key graphic, showing a different color, or group of colors for each data item. So for example, there is one white dot under the signal strength data in column 3. There are 3 groups of 3 dots (yellow, green, yellow) in columns 4-12 representing the frequency data in the format: 999,999,999.
The 2nd blue row from the bottom is a divider.
The next shows which data items are being controlled by modulators. The 3 white LED’s show modulation of frequency data in the million’s, 100’s, and ten’s places.
There are 5 modulator units in the display. Data is represented using a color code..
Gray LED’s represent ‘momentary’ controls in the off state. When a momentary button is pressed, it will blink white.
Here is an example of a modulator unit
The blue LED’s are just dividers (background space)
The first column of data on the left is the on/off indicator and the modulator’s ID number.
The top LED of the column is the on/off toggle. It is blank, which means off.
The next two red LED’s together represent the ID number of the modulator: red = 1
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For the remaining columns, the top row indicates whether the input gate is open allowing other modulators to control the parameter. Grey indicates the gate is closed, A white LED means the input gate is open.
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The second and third columns of data are the clock speed and wave type. The 2 LEDS in each column are grouped together and are using the color code above. The clock speed is 5 (white). The wave type is 4 (yellow)
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The fourth and fifth columns of data are the low and high range. Low range value is 5 (white) and high range value is 2 (green) – which doesn’t make sense, but this is simulator data.
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The last column is the modulator destination activity indicator: grey if zero (not assigned) or white if any non-zero value.
// modulator data structure // these are fixed structures 8x2, with specific color rules // // ulx, uly // mod id number 1-n // on : 0 = off, 1 = on // modin : modulation source index 0-4 // clockspeed : 0-4 // wavetype : 0-4 // lorange : 0-4 // hirange : 0-4 // ingate : 0 - 4 (tells which control is being modulated) // spare // destination : 0-127 destination index // this is displayed elsewhere //
Adafruit 32×32 RGB LED panel
https://www.adafruit.com/products/1484?gclid=CMzrnYDB1b4CFTQQ7AodjXkAFw
files are also in tkzic/new max radio project/
There is a newer version adapted for the Max radio project – basically same code, but file names are
“Build a drawing robot using two servo motors operated by any audio player.”
By Sean Michael Ragan and Mikal Hart at makezine.com