Various Information on Servos V1.01

Contents:


1) Servo Cross-Reference Chart

(From Julio C. Chacon, Jr)

Someone kindly asked me to post this, so here goes.The Novak Input Plug System is very useful if you need to swap plugs to use different servos on different radio systems. The different plug styles in the kit are individually marked. In addition, the plugs are marked "WHT, RED, BLK" in the appropriate order that they should be installed on the plug. for reference, I'll place these at the top of the chart: 

                RED(+)  BLK(-)  WHT(signal)
                ===     ===     ===
Airtronics      Red     Black   Brown
Sanwa           Red     Black   Black [*]
Futaba J        Red     Black   White
KO Propo        Red     Black   Blue
Kyosho/Pulsar   Red     Black   Yellow
Japan Radio(JR) Red     Brown   Orange
[*] I've never seen one, so don't ask!

And there it is! All you have to do to replace the plug is make sure that you place the corresponding wire in the proper location as marked on the connector. For example, if you have a Futaba servo that you'd like to use on an Airtronics receiver, simply take the Airtronics connector from the kit, and and stick the Red in RED, White in WHT, and Black in BLK. If you don't have the input kit, but you have two servos, you should write down the order of the wires as they appear on the Airtronics servo, then remove it. Next, you would remove the plug off of the Futaba servo and install the Airtronics plug by inserting the White wire where the Brown one was, then the Black to Black, and Red to Red. I Hope you make use of it!

By the way, this chart is included with the N.I.P.S.

2) Servo clock source 

                                                    o  5VDC
                                                    |
        5k pot             4.3k                     |
 x---/\/\/\/\/\/--------/\/\/\/\/\-----------x------x
 |                                   ________|______|_______
 |                                  |        4      8       |
 x----------------------------------|7                      |
 |      1N457 diode                 |                       |          output
 x--------->|---------------x-------|6                     3|------------------
 |                          |       |      NE555            |
 |       68k                |       |                       |
 x---/\/\/\/\/\/\/-----x----x-------|2                      |
                       |            |_______1_______5_______|
                       |                    |       |
                      _|_                   |      _|_
                      ___  0.33uf           |      ___  0.1uf
                       |                    |       |
                       x----------x---------x-------x
                                  |
                                  |
                                -----
                                 ---  Gnd
                                  -

3) Servo Driver Circuit needed

Here's a circuit that's older than dirt, but it works quite well.

+V  o-------o--------o----o-------------o----o-------------o-----o +V
            |        |    |             |    |             |
Gnd o    R1-100K     |    |             |    |       R4--> R3    o Gnd
    |       |        |    |             |    |      4.7K   10K   |
    |       |      |--------|         |---------|     |    |     |
    |       |      | 4    8 |         | 5   14  |     |          |
    |       o------|7       |         |       11|-----o          |
    |     R2-15K   | (555) 3|-----o---|3        |  C2-0.22mF     |
    |       o------|6       |     |   | (74121) |     |          |
    |       |      | 2    1 |     +---|4      10|-----o          |
    |       |      |--------|         | 7    6  |                |
    |       |        |    |           |---------|                |
    |       o--------+    |             |    |                   |
    |       |             |             |    +--------- Servo    |
    |  C1-0.22 mF         |             |               Signal   |
    |       |             |             |                        |
    +------ o-------------o-------------o------------------------+

Notes:

  1. R3 is a 10K pot, connected as a variable resistor
  2. Increased value for R1 -> less angular throw @ R3
  3. Servo signal (Pin 6 of 74121) is for 'positive-going' servos (Use signal @ Pin 1 for negative-going servos)

It would be simple to connect an external pot instead of the internal 'feedback' pot (most servos use a 1.5K pot), but you'd still have to provide a means for the pot to be rotated by the gear train. Remember, the servo is a 'closed loop' feedback system.

4) Servo Controller Schematic and Code

This is a PIC16C55-based servo controller project that reads a joystick and adjusts the servo accordingly. Includes source code and a schematic drawn with a free package. Only catch is that the schematic program and all the required PIC programming utilities will ONLY run under MS-DOG.

Servo Controller Schematic and Code

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