Receiver picking up the signal too slow.

[DSpeegle]

I need to transmit a simple on/off signal a very short distance, like 1 ft. I'm using an rf600e/d set with a 434 mhz transmitter/reciever WRL-10534 . I have them wired up to a good omnidirectional antenna thats rated for 434 mhz. I have tested it over 200 ft and it works just fine. The issue I'm having is that I need the signal to be picked up as quickly as possible. Theres currently a good 1 second delay between the transmitter sending it and the receiver showing that it has a signal. What can I do to make this quicker? I don't see why it would have a delay that long.

 

[Comcokid]

There can be a lot more going on in the lower-levels of the transmitter and receiver than you realize. I quickly check the RF600 application sheet, and in addition to 6.4 msec of input debounce I found the following statement:

The data format automatically includes a preamble, synchronisation header, followed by the encrypted and fixed code data then a CRC check. The actual packet size is 67 bits. Each transmission is followed by a guard period before another transmission can begin.

The WRL-10534 also indicates it operates at 4800bps, or bits-per-second. Add up that preamble, sync header packet, CRC, and maybe some additional wait in the receiver for it to determine another packet is not immediately following, and it may add up to a second or two.

If you need low latency in your application, you may need to design at a lower level than just buying a simple module, or select a module that provides all the source code and study and evaluate the chip set before selecting one.

 

[DSpeegle]

What confuses me is that it says that the maximum delay between input pressed and output asserted is 210 mS. That tell me the addition; 800mS is lost in the air or in the modules. Are you saying that it might be transmitting too much data through a slow transmitter/receiver?

 

[MikeHalloran]

Is it possible that you are powering up the device whenever you need to send a '1' bit, thereby suffering delays associated with power-up only, instead of leaving both ends powered and toggling only the data input when you need to send a bit?

Mike Halloran
Pembroke Pines, FL, USA

 

[DSpeegle]

It has power constantly and I don't use the SLEEP mode but... It does power on when it receives the data, which would explain why it responds quickly if i send a second single immediately after the first. How could I keep it alert and ready to go? I've tried constantly sending a signal on one of the other inputs but when I try to to send the input I want, it will only accept it once. I have to power cycle it in order to send the signal again, although it has absolutely no delay. Maybe I could put a pulse wave on one of the inputs so that it is constantly transmitting but its not considered a hold?

 

[MacGyverS2000]

It has power constantly and I don't use the SLEEP mode but... It does power on when it receives the data, which would explain why it responds quickly if i send a second single immediately after the first.

Does not compute... you say you don't use SLEEP mode, but you follow that statement up with "it powers on when it receives the data." What is powering on if it's already on?

Why do you have to power cycle to get an input to work more than once? Sounds like something else is going wrong here...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[DSpeegle]

Sorry, I described that wrong. It's powered on constantly but remains somewhat 'inactive' unless the signal is detected. It's sort of a power saving mechanism. It has a 'sleep' mode but that turns off all of its functions but I'm not using that.

Let me explain what I mean by having to power cycle. The input works just fine normally but has some latency and I'm trying to get rid of that. Once the signal is picked up I can trigger it quickly with no delay. So I thought to myself, why not have a dummy signal constantly going on a dead output so that it never disconnects and I can get that quick delay. While the dummy signal is going I can get my trigger to work quickly with no delay but it only works once in this setup. I have to power cycle it in order to use the trigger again.

 

[VEBill]

Morse code works.

In other words, perhaps you could use less advanced technology (ON-OFF Keying, carrier sense).

The risk is that other signals may trigger your receiver.

 

[MikeHalloran]

Is there some reason you can't use a WIRE?


Mike Halloran
Pembroke Pines, FL, USA

 

[DSpeegle]

Yea, its for an accessory and the product can't have extra wires hanging on it and were trying to avoid drilling into the products. I talked to RF Solutions and they said it's because the modules that I picked are "old" technology and that the delay would be significantly reduced with a better module.

 

[benta]

"I have tested it over 200 ft and it works just fine."
What do you mean by that statement? Is it in this case fast enough?
If so, at a distance of 1 foot, you are probably overloading the receiver AGC, which needs some time to adjust. Try wrapping the receiver antenna in aluminium foil and try again.

Benta.