I have a transmitter module (TVTXL868A04C - Teleco Automation - EN) and I can send some specific commands by connecting one of the output wires with the common wire.
By short-cutting a wire, the module sends a specific command. When being short-cut, there is a very short peek current of about 4mA, followed by a continuous current of about 1.5mA.
If I measure the voltage between the open wire and common I read 25v (?!).
I could use a relay to short-cut the wires, but that means quite some relays (multiple modules, multiple wires). It feels like overkill.
Could I configure an Arduino-output as pull-up and connect the transmitter wires directly to the Arduino?
Then when putting the Arduino output to LOW, it should short-circuit the transmitter wire, and the signal should be sent.
The thing is, when I just take an Arduino, do not connect anything, not even a USB cable, and then I connect the transmitter cable and common to an Arduino digital pin and the ground pin, the power led of the Arduino starts glowing a bit... So current from the transmitter is flowing into the Arduino.
Guess this approach isn't that sound?
Should I use a transistor?
Any ideas on that, if needed? My lessons of electronics are far far gone... :o
Thanks!
Yes, you are powering the Arduino through the GPIO pin. You can't apply a voltage to a GPIO that is higher than the voltage on the Atmega328P's Vcc pin, which is usually 5V when powered up, but zero volts when powered down. So no, you can't do this directly from the Arduino. You'll need an NPN transistor which is controlled from the GPIO pin through a base resistor (10K or so), the collector connected to the control line, and the emitter connected to common ground.
But I dont understand why you are seeing 25V. The link you provided says the control lines should be 12V. Are the Arduino common and module common connected?
first off WELCOME !
Welcome to the forum.
Fom your link it appears that the device has an internal power supply that gets 12v from the 230 volt mains power.
It also appears that it is a radio receiver that is part of a larger system.
I could not find any data sheets or instructions on which side this goes. The transmitter side or the receiver side.
If this is the transmitter side, then what you will need to do is to control and switch that without any possibility of that 12v getting into your Arduino.
I would recommend using an opto-isolator so your Arduino powers the signal side and the power/logic side is connected to your device.
you can get opto-isolators rather inexpensive and they come in different ratings. make sure the power side can handle the 24 volts you noted.
by using an optoisolator, there is no connection between the two devices.
ShermanP:
Yes, you are powering the Arduino through the GPIO pin. You can't apply a voltage to a GPIO that is higher than the voltage on the Atmega328P's Vcc pin, which is usually 5V when powered up, but zero volts when powered down. So no, you can't do this directly from the Arduino. You'll need an NPN transistor which is controlled from the GPIO pin through a base resistor (10K or so), the collector connected to the control line, and the emitter connected to common ground.
But I dont understand why you are seeing 25V. The link you provided says the control lines should be 12V. Are the Arduino common and module common connected?
Yes, the 25v is strange, but that is what I read between any channel wire and the com wire.
I did connect the Arduino common (gnd) and the module common together.
I will try your suggestion with the NPN transistors.
Thanks a lot!