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Electronics

Radio control system (modification)

dscn4545 [240x133]The radio control with the help of a remote control is good, but ... this model of awning does not have a crankshaft to handle it in the event of failure of this system.
This is why I was led to think about a solution which brings me comfort and security at the same time.

First of all, no need to search the Internet to find the diagram of this device, it does not exist. I had to recreate it in order to be able to carry out my project.

Operation detail:

The diagram of the original device that I was able to recreate has a radio module ( HY1 ) operating at the frequency of 433 MHz, which makes it possible to receive orders from the remote control.
The digital information available at its output ( pin 14 ) is sent to a micro-controller ( IC3 ) of Microchip type PIC16F622A ( pin 12 ) for processing. A quartz oscillator clocked at 4 MHz provides it with its clock frequency. It also has two inputs ( pins 10/11 ) and two outputs ( pins 1/18 ) but only pins 1 and 18 are used. The inputs are sent to a connector ( X2) via protection diodes D5 / D6. These two inputs can optionally accommodate push buttons to replace the remote control functions.
I could not read the contents of the ROM-Flash, this one being protected. The processor uses an EEPROM type 24LC01 ( IC4 ) to save its data and of course has its own I²C Bus for its management. In fact and in front of this impossibility of reading the software, impossible for me ( or for anyone ) to modify it to add some additional routines. This is why I added my Bus to this board.

executable  PROJECT INFO
  Types of components: Traverrsants
                                         and CMS
  Level: ◆◆◆ ◇◇
  Construction time: 2 to 3 hours
  Cost: approx. 20 €

The supply voltage supplied by the transformer ( TR1 ) is limited to + 17.6V c / c ( measured voltage ) via the transil diode D3 before driving a regulator IC1 ( LM78L05 ) supplying the + 5V to the whole circuit.
A little reminder about the function of diode D4:
It only serves to protect the voltage regulator IC1 and thus prevent its destruction in the event of disappearance of the voltage normally present at its input. In fact, in this case, the input being found close to zero volts, and the output still positive and therefore with a potential greater than that of its input, there is a risk of destruction by reverse polarity on this regulator. This can especially happen with the use of electrolytic capacitors of high values ​​on the output, which is not the case here. The assembly articulated around the transistor T1 ( BC846 ) allows three things:

  1. detection of the presence of the supply voltage via diode D1 ( LL4148 )
  2. Auto reset function when power on
  3. save the registers and other data necessary for the operation of the microcontroller ( Power_Save info )

The two outputs of the microcontroller ( RA1 and RA2 ) are used to drive the two relays ( K1 and K2 ) via transistors T6 and T7.
The functions of these relays are as follows:

  • relay K1: reversal of the winding direction of the fabric on the blind cylinder
  • relay K2: activation / deactivation of the motor allowing the operation of the blind

It should be noted that a time delay of 150 seconds ( measured period ) automatically deactivates any command delivered by the microcontroller, in order to avoid activating the relays permanently.
This delay may seem very long compared to the time ( I counted a little less than 45 seconds ... ) allowed for the awning to go out or in ...

 
Radio control AUTOMO5 modified ...
Note that the whole part of the diagram surrounded by dotted lines represents the circuits that I added for my project.

Explanations:

My project consists of using a programmable controller of my own to be able to automatically control and thus place the blind in safety in the cases described below:

  • in case of too strong wind, immediate retraction of the awning fabric
  • in case of rain, immediate retraction of the awning fabric
  • in the event of sun, take out the awning fabric ( optional, I still have some difficulties with a sensor )

The first two functions have priority and it is then necessary to inhibit the original functions, even if the remote control is handled during these cases.
This is made possible precisely by the assembly shown inside the dotted lines. An IC5 port expander ( PCF8574A ) has been added and receives its orders via the I²C Bus ( RJ12 X5 * 1 and X5 * 2 sockets ).
And why 2 RJ12 sockets? simply to be able to connect the incoming cable coming from the management card which is remote, and the other to be able to connect the wind detection module.
I will also need a third for the rain detection module, when the time comes I will adda small box containing all these sockets.

The expander circuit ( IC5 ) has three outputs which are used to block the operation of the micro-controller ( IC3 ) and to drive the two relays. The operating logic is as follows:
at rest therefore without a command from the I²C bus, all the outputs of IC5 are by internal design ( Pull-Up resistors ) in the high logic state ( + 5V ). The transistor T3 is blocked because of its basic bias. Thus the transistors T4 / T5 are also blocked since their collector voltage is almost zero.

  • if any order is received via the I²C Bus:
    • the software embedded in the management card generates a low logic state on the P0 output of IC5
      this causes the PNP transistor T3 ( BC557 ) to become conductive because of its base bias ( it is blocked at rest ), the NPN transistors T4 / T5 ( BC547 ) thus see their collector voltage tend towards + 5V. They are ready to process future orders.
    • the high logic state available on the collector of T3 polarizes the base of T2 NPN ( BC547 ) which becomes conductive. Its collector suddenly goes to the low logic state, which implies that the MCLR pin of IC3 also goes low. The microcontroller is blocked until this pin goes back to the high state causing a reset.
     
A few comments :
  • the three jumpers SJ1 / SJ2 / SJ3 are used to define the address of the expander ( IC5 ) on the I²C Bus. I chose the address 0x76 ( 0b0111011X ) because it is a PCF8574 A ( see its datasheet)
  • D7 / D8 / D9 / D10 diodes are Schottky diodes serving only for protection. They are necessary to avoid, for example, unexpected escalations to the ports of the micro-controller
  • I replaced the tantalum capacitor C2 2,2μF / 20V a 4,7μF / 20V same technology because I was getting far too much residual ( ~ 6.8V ) on a rectified voltage ( half-wave ) peak to peak of + 18.4V c / c ! With the 4.7µF I obtain a residual of 3.20V for the same value of rectified voltage. I made this modification because this type of tantalum capacitor being much less reliable over time than an electrolytic model, I preferred to replace it.
  • The value of the voltage measured at the terminals of the Transil D3 diode ( SMBJ20A ) is + 17.54V eff , no load , ie without maintaining the relays.
    When the two relays are stuck it goes down to + 12.82V eff .
  • I added a 10µF / 16V tantalum capacitor ( C9 ) to the output of the 5V regulator ( IC1 ) because it did not exist at the factory. In fact the range of reception of the AUTOMO5 varies a lot since last year according to the ambient temperature, and that makes me think of a capacitor and therefore a voltage which would change value. To be tested over time ...
  • the supply in + 5V ( + 5VA ) of all the circuits included in the dotted area is done via a regulator 78L05 ( IC2 ), which takes the voltage of + 12V through a fuse and diode D2 on the I²C Bus cable, as for the wind detection module. I had in the article describing this module already explained this particularity of wiring.
    Note the + 5VA is not connected to the + 5V of the AUTOMO5 board.

 

and pictures ...

 Board AUTOMO5 zoom on C2 ...Board AUTOMO5 zoom on C9 ...Board AUTOMO5 zoom on D7 and D8 ...Board AUTOMO5 zoom on D7 ...Board AUTOMO5 zoom on D8 ...
PCF8574 Board (Top)
AUTOMO5 modifiedAUTOMO5 modified zoom ...

Packages comprena nt : save f2
Schematic diagram ( without PCB ) drawn in Eagle v7.7.0
some pictures I took during my changes

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