a "do everything"module

(update of the 26/10/99)

I propose here the electronic swiss-knife for remote control. It is a module to do everything being able to serve as:

  • - beeper in the event of loss of a nice sailplane in a not less nice field of corn (lived experiment)
  • - ordering of relay, light or other...
  • - command forward / reverse gear in "all or nothing" for small engine,
  • - flashing indicator with 1 Hz and 1/4 Hz (two outputs). Output GP2 (see further) can be used on radios PCM with fail safe at the reception as beeper model loss.

Well that does not make coffee but I'm thinking to improve it !

Super, but, that must be bloody complicated...

Not at all, that weighs less than 10 grams! You need:

  • - a servo cord,
  • - only one electronic component (PIC 12C509) 3 Euros microcontrolor...

in addition, according to what you want to control :

  • - a piezo buzzer for SOS model function (to be recovered on a toy or buy it 15 to 20 F at radiospares)
  • - one or two very high brigthness LEDs, for example for the side-lights (5 to 50 F at radiospares according to the model) (plus a limitation resistance )

Since one wants to tackle power that becomes a little bit more complicated (I said a little ...):

  • - a relay and its interface with transistor or only one transistor to turn an engine ON
  • - a relay for the inversion of direction of rotation of the engine (reverse gear)

the realization

For simplest functions (flashing indicator and/or beeper) you don't need a printed circuit board, directly weld onto the legs of the PIC, an end of heat-shrinkable sleeve and that is.

Go ahead with softness if you do not want to burn the integrated circuit (do not use an iron of more than 30 W)! Do not rectify the legs of the circuits, that weakens them, you will be likely to break them or worse than they break later in flight...

For the remainder, I deliver the diagrams and it is up to you to make a printed circuit if you wish , or to use a piece of board with holes.

Some remarks on the diagram:

  • - the reference mark of the integrated circuit is to the top, the circuit is seen top...
  • - I represented standardized connectors (Graupner, hitec or Futaba) for the others consult this extremely well made page.
  • - the buzzer is polarized, if you cross wire that will not run and I do not know what happens with the buzzer (do not test!)
  • - I put a LED connected on the output flashing indicator 0,5 seconds. Of course it is not necessary if you do not want the flashing indicator! On the LED the + is the longest leg (side GP2 on the diagram).

    Knowing that the microcontrolor can deliver 25 mA max by output, if you want to put several LEDs, they should be fed in series and not in parallel

  • For a strong luminosity, resistance in series on the LED can be changed by one 220 Ohms (the current output under 5V is then 22mA and remains compatible with specifications )
  • For PCM radios with fail-safe at the reception, the loss of the transmitting signal is detected by the receiver. The position of the channels is maintained during the loss of the transmitting signal by receiver itself. Thus we can't detect a loss of the model by turning the radio OFF. With this kind of radio, I thus advise you to fulfill the function " loss model " on leg GP2 " flashing indicator 1/4 Hz ". The black wire of the buzzer will be connected at "minus -", the red wire with GP2. When you lost your model, think of rocking the switch starting the beep sound! After power on reset, the buzzer will sound during 5 seconds.

All that it is quite beautiful, but where to find the PIC? Two options still:

- to program yours starting from HEX file provided here (2 versions are given : one for 12C508 PIC the other for the 12C509) , or even compile the C source also provided (but I ask you not to market it).

- to contact me to obtain ready-programmed one ...

For more information on the PEAK, best, it is to go directly to manufacturer MICROCHIP.

how does it work?

Imagine that, compared to the neutral position of a radio channel (depth example), one has two positions to the top, two positions to the bottom and the neutral; the circuit functions as follows:
all in top

GP5 = 1: buzzer silent
GP4 = flickers at 1Hz
GP2 = flicker at 1/4 Hz
GP1 = 1: engine ON
GP0 = 0: go forward

high medium

GP5 = 1: buzzer silent
GP4 = 0
GP2 = flicker to 1/4 Hz
GP1 = 1: engine ONE
GP0 = 0: go forward


GP5 = 1: buzzer silent
GP4 = 0
GP2 = 0
GP1 = 0: engine OFF
GP0 = 0: go forward
make an attempt of a 300 ms deadline (for brake of propeller...)

low medium

GP5 = 1: buzzer silent
GP4 = 0
GP2 = 0
GP1 = 0: engine OFF
GP0 = 1: reverse gear

all in bottom

GP5 = 1: buzzer silent
GP4 = 0
GP2 = 0
GP1 = 1: engine ON
GP0 = 1: reverse gear

transmitter OFF (model loss) 

except radios PCM

GP5: The buzzer sounds at the rate of three seconds ON, three seconds OFF
all the remainder is at 0

with the setting ONE

GP5 = 0 during 5 seconds (buzzer sounds)
GP2 = 1 during 5 seconds: if a buzzer is connected, it sounds (radios PCM)

Now, if you do not wish to use the functions related to the reverse gear, it is enough to put the handle, the linear potentiometer or it inter radio in low position.

After the 5 seconds of adjustment of the neutral, there will remain to you only the functions associated to the two positons to the top and to the neutral in bottom.

in practice:

              WARNING: turn ON the radio (the transmitter) first, then turn ON the
              receiver. After power ON reset, leave your radio to the neutral during
              approximately 5 seconds. It is during these 5 seconds that the microcomputer
              calculates duration N of the neutral of the connected way.

              During this phase of calibration of the neutral, a continuous beep is heard.(output
              GP5 = 0). In the same way, output GP2 is maintained at 1 during 5 seconds. (One
              thinks of the radios in PCM with fail safe...)

              Once this phase of calibration of the neutral passed, the device functions.

It is not more complicated than that. microcontrolers, it is big foot !

Should you have some good ideas to add to this device, don't hezitate to contact me. Everything can be done with a PIC !


how to connect a relay :

you need :

  • - a 4,7 k resistor
  • - a diode
  • - a NPN transistor ex 2N2222
  • - a 5 Volts elay

connect all that as follows : (bottom view of the 2N 2222)

usuall precautions :

The devise was tested successfully on several radio devices (Futaba, a NPM receiver, an old 2 channels AM radio, a MULTIPLEX one...) It should work on any type of hardware but is up to you to check it!

In the same way, I decline any responsibility in the event of damage caused to your hardware following a bad wiring or other defect...