Using to control 27Mhz RC toys

[xromansx]

Hi, do you know if it can be used to do 27Mhz pulses to control cheap RC toys. example of signal from other project: { "name": "jsbr RC Car", "description": "Ford Mustang, 40MHz, No. 23819", "frequency": 40.0, "synchronization_burst_us": 1200, "synchronization_spacing_us": 500, "total_synchronizations": 4, "signal_burst_us": 400, "signal_spacing_us": 400,

"forward": 11, "left": 59, "forward_left": 27, "right": 64, "forward_right": 33, "reverse": 39, "reverse_left": 51, "reverse_right": 45 }

[jakeson21]

Maybe, but you'd need to look at the datasheet for the minimum frequency switching time. Also, It's an oscillator and not a pulse width generator, which sounds like what you really need. An AT-Tiny / Arduino / Node-MCU may be a better fit here - and offer a lot more control options. https://www.nodemcu.com/index_en.html#fr_54747661d775ef1a3600009e

[xromansx]

Thanks for reply I wanted to use https://github.com/papadeltasierra/dma433 to modulate the signal and LTC6904 to transmit it would it work like this or I'm missing something.

[jakeson21]

This probably won't work, since the LTC6904 is really only meant to drive a standard TTL input. It won't be able to provide enough current to radiate very far, it at all - you would need to feed it into an RF amplifier, and the output is not very clean. Also, at those frequencies you'd need to carefully design a circuit board for this chip. Are you trying to make a generic radio controller?

Another option is to use a pre-build solution: 27MHz modulator on ebay

[xromansx]

sort of, but I would like to be able to switch between 27 and 49Mhz, I'm trying to do something similar to https://github.com/bskari/pi-rc but with arduino or esp32.

[jakeson21]

This will likely not work. Why not use a Rpi and make use of pi-rc? If arduino is what you want you may need to look at a Teensy and use the IntervalTimer library as the Arduino isn't even close to being fast enough to do this.

[xromansx]

This guy https://www.riyas.org/2014/06/computer-controlling-27mhz-remote-control-car-ad9850-dds.html made a project on arduino and it's working good. Was thinking maybe esp32 can do it through this chip, but ad9850 doesn't support 49Mhz and I need this frequesncy also.

[jakeson21]

Actually that would be perfect. From the spec sheet "The AD9850’s circuit architecture allows the generation of output frequencies of up to one-half the reference clock frequency (or 62.5 MHz)". This one uses a 125MHz oscillator, so 47 MHz is within the range. The ESP32 has a much faster clock speed (2x to 4x) than a standard Arduino Uno.

[xromansx]

I'll try to do it with si5351 still don't understand why it's not realizable with LTC6904 and external amplifier.