Control – Smallest Delay Possible in RF Remote Control


I have a very basic knowledge on electronics but that's it. so I don't know this topic well. Altho, I'm able to assembly a circuit , check it and make it work.

I've been searching for info about RF remote controls and their delays.
Seems like 434 mhz and 2.4 ghz, they all take no less than 2,5 to 5 ms between the moment the user push a button in the transmitter an a signal is produced in the receiver. But I don't know if I'm right. so If any would know about it is you guys. I want to know before losing more of my time searching for something that's not there.

The reason to ask this is that I need the delay to be 1 ms or less. For all the people wondering "why would you even need the delay to be 1ms", just agree with my by now. (yeah we know that humans are slow , and "nobody in the universe will need a 1ms delay device)

What the RF needs to do i simple: Once a button is pushed , the receiver must send a High voltage signal and that will happen aprox each 1,8 secs for no more than 20 times.

My question is:

Is there any RF transmitter-receiver with standard wireless technology that gives 1 ms delay?

Thanks in advance.

The following is some of the info I've found about the delay in some RF transmitters – receivers.

About the RX3400 model (a 433-MHz)
the only info i've found in the data sheet is:
Turn on time: 20mS from power is switched on.

I'm not sure if i should use this info as the remote will be already on?.

This article talks generically about the LPD-type 433-MHz FM transmitters.
(I'm not sure if those times are standard)

it says it takes 4-ms time slot to transmit. so from there the delay will be >4ms

In another article this 433mhz transmitter-reciever is used with an arduino:

For an RF bit rate of 2000 bps, need 500microsec bit period.The ramp
requires 8 samples per bit period, so need 62.5microsec per sample =>
inter-rupt tick is 62.5microsec.The maximum message length consists of
(6 + 1 + VW_MAX_MESSAGE_LEN) * 6 = 222 bits = 0.11 secs (at 2000 bps).

I'm not sure there what would be the minimum length but it seems like the whole proccess is going to be more than 1ms or 2 ms. in my case the order will be one and very simple.

Now this 2 way 2.4 GHz transceiver (it's a development kit):

it says th delay could be about 2,5 ms. but the delay includes (if i understood correctly ) timing the data back to the transmitter. (read below) So If i only need it one way this could work for me?

(the nRF24L01) and an 8-bit MCU (See Figure 4.) The RF module supports
up to 49 button inputs plus status LEDs. In low latency mode, when a
button is pressed the device (the remote control) powers up, transfers
the command input to the host (USB dongle) and receives data back if
requested. This cycle takes around 500 μs. If the first communication
attempt is not successful, the protocol utilises the automatic
acknowledge and re-transmit features of the nRF24L01 to retry
communication on several frequencies. Lab tests at Nordic have shown
that in the typical domestic environment the system will need to
re-transmit 4 to 5 times giving an average latency (including RF power
on and link up) from button press to data acknowledgement by the USB
dongle of 2.5 ms. If the remote is in the presence of a strong Wi-Fi
(802.11g or 802.11n) interference, this latency increases on average
to 3.5 ms

Best Answer

Forget all the "noisy" comments. I wonder if they have even read your info.

The answer is YES. You were pretty close with 2,5 ms with the RF24L01 circuit. But it's a two way remote control. to reduce that time use a one way RC. use a similar circuit with the rNF2401. the delay will be: 200 Micro seconds (transmitter) + 200 Micro seconds (receiver) = 400 Microseconds.

The PLL is run at 2.45GHz with a 1MHz channel resolution. Start up times is in the order of 200μS from standby mode. The VCO incorporates an automatic calibration routine that selects the right frequency of operation. Internal inductors are used for the VCOs which allows excellent control of frequency operation and phase noise. All RF parameters are programmable and are contained in a stand alone RF configuration register. Programming is via a 3 wire SPI. Transmitter Typical Operation. The external MCU interfaces with the following pins: CE (Chip Enable), CLK1 and DATA. When the application MCU has data to send the CE pin is set high. This activates nRF2401 on-board data processing. The address of the receiving node (RX address) and payload data is clocked into the nRF2401. The application protocol or MCU sets the speed. The MCU sets the CE pin low; this activates a nRF2401 ShockBurst™ transmission. The RF front end is powered up, the RF packet is completed (preamble added, CRC calculated) and the data is transmitted at high speed (250 kbps or 1 Mbps configured by user), finally the device returns to stand-by mode when finished.

Receiver Typical Operation. The MCU interface pins: CE, DR1 (Data Ready 1), CLK1 and DATA (one RX channel receive mode). To activate RX, the CE pin is set high, after 200μs settling the device is monitoring the air for incoming communication. When a valid packet has been received (correct address and CRC found), nRF2401 removes the preamble, address and CRC bits. It then notifies (interrupts) the MCU by setting the DR1 pin high. The data is available for the MCU to clock out. When all of the payload data is retrieve d the device sets DR1 low again and is ready for a new incoming data packet.