I am now 80 years old and my medical condition is deteriorating, so I have decided that my designs should be documented to allow others to build my U/Tronics Control (U/T) units. I will start with the single-channel unit, with the multichannel (four to seven channels) encoder and decoder units to follow. I coined the name U/Tronics Control in 1982. U/Tronics Control stands for U/Control (Control Line or CL) with electronics added. All UT units are designed for use with standard, not digital, servos.
To verify the accuracy of these instructions, I asked Mike Boucher if he would build a set of units if I supplied all of the material. Mike agreed, and after each unit was built, he shipped it to me for testing. All three units that Mike built worked right out of the box.
I want to thank Mike for taking on this project. There are three other people who deserve a big thank-you: Mike’s wife, Robin, and his daughter, Rachael, for allowing Mike to do this, and my wife, Pat, who has put up with my hobbies for 55 years. Thank you, ladies!
The typical use of a U/T single-channel unit is for throttle control for your CL model without needing to switch to a three-line control system. It even works if the insulated lines are slack! They can be used in CL Scale, CL Navy Carrier, and CL sport flying.
When teaching a new or rusty pilot, if he or she gets dizzy, you can slow the airplane or cut the engine completely and land. It is fun to do multiple touch-and-gos in a single flight.
The U/T single-channel unit is controlled by varying the resistance between the brown and green wires with 0 ohms giving an output pulse width of 0.9 milliseconds every 20 milliseconds and 10K ohms, giving an output pulse width of 2.1 milliseconds every 20 milliseconds. This will control almost any analog servo or ESC.
Study the pictures while reading the instructions. I have 60 years of experience in electronics, so I will try to not leave any “obvious” steps out.
Saw the board from the prototyping perfboard material, and make sure the saw teeth cut from the circuit (copper) side first. If cutting from the component side, copper paths may be pulled from the board.
I cut the boards by sawing through the next set of holes and then filing the edges smooth. You can make seven boards at a time from the 35 paths across the prototyping perfboard.
Select and bevel one corner as shown in Drawing 1. This will give you an index mark to know which end is up when you turn the board over. You can put paint or tape on the corner to serve as an index marker if you wish.
Following Drawing 1, cut the copper paths in seven places. There is .06 inch of space between holes. Try to remove .015 to .02 inch of copper centered between the holes. I use a sharp #11 blade and pull it firmly twice across the path in two places and then use the point to pick the copper off the board between the cuts.
Using a permanent marker, mark the location for Pin 1 of the 555 Timer IC on the component side of the board at the hole indicated in Drawing 2.
Inspect the board to verify that the paths are completely cut and a gap exists between the ends of the cut paths. The best way is to hold the board up with the circuit side toward you in front of a bright light.
Note that all jumpers, components, and wires are inserted from the component side and soldered on the circuit side of the board. Always wipe the old solder off of the soldering iron tip before soldering each wire or component. I use a damp cellulose sponge to wipe my soldering iron tip. Do not exceed 10 seconds on any one solder joint!
Cut to length, form, install, and solder two bare wire jumpers per Picture 2 and Drawing 2. After soldering each component or wire, trim the excess length flush with the solder on the board’s circuit side (see Picture 2).
Cut to length two insulated solid copper-wire jumpers, strip both ends 1/4-inch, then form, install, and solder as shown in Picture 2 and Drawing 2. Form the insulated wires around, not across, the bare wires.
Warning: Before handling any integrated circuit (IC) or transistor, always touch a grounded piece of metal to reduce the chance of static electricity damaging the IC or transistor.
Proper IC orientation is determined by the location of the indexing notch in the end of its case, which is at the pin 1 end of the package. Insert the 555 Timer IC on the component side of the board with pin 1 in the proper hole. Start one row of pins in their proper holes, then using the back side of an X-Acto knife blade, press the other row of pins inward to allow them to enter the correct row of holes. The spring tension in the pins will hold the IC in position for soldering.
Verify that the pins are in the correct holes and that the IC is down against the board or wires that pass under the IC. Solder the IC pins on the circuit side of the board. Visually inspect the board for solder bridges between paths.
Form the leads for each component per Picture 3 and install and solder as shown in Drawing. 2. Install the 1N4148 or 1N914 diode with the black band located as indicated on Drawing 2 and solder.
Cut a 1/4-inch length of heat-shrink sleeve and slide over one lead of the 180K ohm resistor and against the resistor’s body. Make two bends in the sleeved lead per the pictures. Make one bend in the other lead and install the resistor in its holes as in Drawing 2 and solder.
Form the leads of the .01 mf capacitor per the pictures. Install as in Drawing 2 and solder. Form the leads of the 6.2K ohm resistor per the pictures, install it as shown in Drawing 2, and solder. Install the .15 mF capacitor per Drawing 2 and solder.
Cut to length, strip, and tin 3/16 inch of one end of the following wires:
Black No. 24: 5 inches
Black No. 24: 4 inches
Red No. 24: 5 inches
Red No. 24: 4 inches
Brown No. 26: 4 inches
Green No. 26: 4 inches
Yellow No. 26: 4 inches
Install the wires one at a time and solder per Drawing 2. Visually inspect the board for solder bridges between paths and form the wires as shown in Picture 4. Twist the wires together in three sets: green and brown to the 10K ohm potentiometer, red and black to the 4.8-volt battery, and red, yellow, and black to the servo connector.
Trim the three wires for the servo connector to the length of the shortest one. Strip and tin the wires 1/8 inch. Cut three 3/8-inch lengths of 3/32-inch heat-shrink sleeves and slide one over each wire. Push the material back out of the way.
Cut three pins from the 40-pin header. Tin the short ends of the header pins, and solder the three wires to the short end of these pins. Red should be soldered to the center pin, and the black and yellow wires to the outside pins. Cover the solder joints with the heat shrink sleeve and shrink in place. Strip and tin 1/4 inch of the four remaining wires.
Visually inspect the board for solder bridges between paths and make sure that all components are properly soldered to the circuit board. Use an ohm meter to measure the resistance between the red and black wires that go to the 4.8-volt battery. This number must be greater than 6K ohms. If not, repeat step 21 and also verify that all component leads and wires are in the correct holes.
Temporarily tack-solder the brown and green wires to a 10K ohm potentiometer. Connect and solder the red and black wires to a mating connector for a 4.8-volt battery pack. Plug in the battery pack. If there is no smoke, plug in an analog servo and see if it follows the potentiometer. The control signal for the servo is on the yellow wire.
If the servo cable colors are black, red, and white, the white wire mates with the yellow wire. If the servo cable colors are brown, red, and orange, the orange wire mates to the yellow wire. If the servo does not follow the potentiometer, verify that the servo is correctly plugged in. If it is, repeat step 22 and look for shorts between component leads on the component side of the board.
When you have it properly working, coat the unit with two coats of Plasti Dip for tool handles. Before you buy the Plasti Dip, shake the can. It should slosh around. If it doesn’t, do not buy it because it is probably expired.
After opening a can of Plasti Dip, reseal it with a piece of aluminum foil covering the top of the can and extending partway down the sides. Secure it with the provided plastic lid. The lid alone will not prevent the solvent from escaping. When finished, the unit should weigh approximately 8 grams.
When you are finished watching it operate, unsolder the green and brown wires from the 10K ohm potentiometer. Install the U/T single-channel unit in your model with a servo to control the throttle on your engine and a 4.8-volt battery pack.
If the battery is located inside your model, be sure to provide a charging jack wired between the on/off switch and the battery. Connect and solder the green and brown wires to a two-conductor connector. Add a mating connector to your insulated flying lines. Mount the 10K potentiometer on your handle and wire and solder it to a two-conductor connector. Add a mating connector to your insulated flying lines. I use 2.5mm miniature ear phone jacks and plugs.
If you plan to use the unit in an electric-powered model with an ESC mount, put the single-channel unit in a box inside the handle and connect the red and black wires to a 4.8-volt battery. Connect the yellow and black wires of the servo connector to your flying lines, and at the model to the ESC signal and ground. Connect the two outside pins.
Instructions for building the multichannel encoder and decoder units can be found on www.ModelAviation.com in the “Features” section. Welcome to the world of U/Tronics Control!