Controlling devices through RS232

Thread Starter

RichW

Joined Nov 8, 2019
5
I have a quick question if anyone can help. If I want to connect a computer to an amp with RS232 and one power output (BNC), then connect the amp to 8 switches, can I then program the amp to choose which switch is turned on?

So if the amp was connected to 8 devices I could then control them individually.

Maybe the switch unit would need RS232 and not the amp? So the computer tells which switch to turn on and the power goes straight through from the amp (i.e. the amp is always on).

Sorry if this is a dumb question I am new to RS232 and it is difficult to find something because I don't know what to look for. Thanks for your help.
 

MaxHeadRoom

Joined Jul 18, 2013
19,683
It depends on what present hardware is in the amp and whether you can implement RS23.
If RS232 can be implemented, it is relatively easy to control or simulate 8 switches.
You need to obtain the info on the amp, and also bone up on RS232 as a means of transmitting and decoding the data.
One way is a small Microchip at the amp end to decode the data.
Max.
 

Thread Starter

RichW

Joined Nov 8, 2019
5
Thanks Max for your answer. It just says "RS232 port for GUI or other digital communication".

If one signal (down one power line) is sent to the switches how will the amp determine which switch to send it to? Wouldn't the system of switches need to be controlled and not the amp?

I have read some things on RS232 but I am still trying to figure out which software would work best.
 

MaxHeadRoom

Joined Jul 18, 2013
19,683
The (serial) form of data sent would need to be decoded at the amp end, and this of course would dictate your transmission format.
RS232 is typically 8 bits of data, some typical industrial standards of transmission methods are Modbus Canbus etc.
Where one end of the system already has its own dedicated format, then the complementary send/recieve end has to conform to this.
Max.
 

Thread Starter

RichW

Joined Nov 8, 2019
5
Thank you for the explanation, I understand now. I will go and do some more reading on this, appreciated!
 

MrChips

Joined Oct 2, 2009
19,913
I think you are confuscating different topics into one topic.

1) You have an amp with some form of serial communications (RS-232) to control some function that is not yet clear.

2) You want to multiplex the output of the amp to one of eight channels.

3) You need someway to select the desired output channel.

You can ignore the concept of RS-232 for the moment. You need to focus on a 1-line to 8-line multiplexer (or switches). Then you need to choose a method of controlling the multiplexer. There are many ways to do this and RS-232 may not be your best choice.
 

MisterBill2

Joined Jan 23, 2018
4,846
Most of the information needed is missing in the posts. Since the amplifier has a BNC output connection I wll presume that it is an RF amplifier, but nothing in your post says that. And we are not given even one word about what the power level from the amplifier is, and so we have no idea what it will take to direct those outputs. AND we have no clue as to what you want to use to switch those outputs. Decoding a serial data signal takes some logic, and that requires some hardware as well as some code. Some brands and models of amateur radio power amplifiers do offer the ability to send the output to different connnectors on the back of the amplifier, That decoding is done in the microcontroller inside the amplifier. I don't think that would be simple to change to add more outputs.
But this is all a guess because the information is not provided.
 

Thread Starter

RichW

Joined Nov 8, 2019
5
I think you are confuscating different topics into one topic.

1) You have an amp with some form of serial communications (RS-232) to control some function that is not yet clear.

2) You want to multiplex the output of the amp to one of eight channels.

3) You need someway to select the desired output channel.

You can ignore the concept of RS-232 for the moment. You need to focus on a 1-line to 8-line multiplexer (or switches). Then you need to choose a method of controlling the multiplexer. There are many ways to do this and RS-232 may not be your best choice.
Yes, I am getting a little confused to be honest.

1. Yes, 2. Yes, 3. Yes. Exactly!

Yes, I thought that I would need to control the switches (multiplexer) and not the amp but wasn't sure. Although I guess I could use the amp to control the type of signal from the amplifier, which could be useful in future. Thank you for the help Mr Chips.

Most of the information needed is missing in the posts. Since the amplifier has a BNC output connection I wll presume that it is an RF amplifier, but nothing in your post says that. And we are not given even one word about what the power level from the amplifier is, and so we have no idea what it will take to direct those outputs. AND we have no clue as to what you want to use to switch those outputs. Decoding a serial data signal takes some logic, and that requires some hardware as well as some code. Some brands and models of amateur radio power amplifiers do offer the ability to send the output to different connnectors on the back of the amplifier, That decoding is done in the microcontroller inside the amplifier. I don't think that would be simple to change to add more outputs.
But this is all a guess because the information is not provided.
Yes, it is an RF amplfier. The power from the amp initially will be 100 W. Thank you for the information on the amateur radio aspect and the difficulty, I think I will now focus on the mutiplexer (switches).

I did some research, a multiplexer has several inputs to one output, I need the opposite, one input to several outputs; a demultiplexer (DMUX). I have seen the truth table and it looks ideal:

https://www.electronicshub.org/demultiplexerdemux/
Would RS232 be a bad choice for comtrol of the DMUX? Or if not could someone recommend a better method of control? Thanks.
 

MrChips

Joined Oct 2, 2009
19,913
If you need to switch 100W on an RF amplifier then you need to look for switches designed for RF power.
For that application, MUX or DMUX is the same thing, 1-to-8 or 8-to-1 is the same.
 

MisterBill2

Joined Jan 23, 2018
4,846
Designs for Selector switches for connecting to different antennas are published frequently. Most of the ones intended for power levels above very low power use electrical relays rated for the voltage and current involved to do the switching, and mostly they use a rotary switch to send the power to the correct relay coil to select a specific output connection. The reason to use a rotary switch is to assure that only one is selected. Most of the designs published in amateur radio magazines can be duplicated with only a moderate amount of effort and skill.
 

Thread Starter

RichW

Joined Nov 8, 2019
5
Designs for Selector switches for connecting to different antennas are published frequently. Most of the ones intended for power levels above very low power use electrical relays rated for the voltage and current involved to do the switching, and mostly they use a rotary switch to send the power to the correct relay coil to select a specific output connection. The reason to use a rotary switch is to assure that only one is selected. Most of the designs published in amateur radio magazines can be duplicated with only a moderate amount of effort and skill.
Thank you Mr Bill, this is really appreciated. My initial idea was to have a power splitter and control that, but they are really expensive.

I've had a look for aerial switches and it seems, like with the power splitter, isolation is an issue. I find this interesting because if one of the aerials hits resonance it acts like a short! So they have to be very well isolated. This one looks very interesting:

http://www.arrl.org/files/file/QEX_Next_Issue/2014/Mar-Apr_2014/Dzado.pdf
 

LesJones

Joined Jan 8, 2017
2,437
The link in your post #11 is for switching receive antennas. You cannot short the output of the transmitter or leave the output open the way the design in your link works. It has to be connected to a 50 ohm load. You do not say if the switching has to take place when the amplifier is giving an output. You also do not say what frequency you are talking about The design for 1.8 Mhz would be very different than for 1296 Mhz (The highest frequency I have worked with.) The design of the part to take the RS232 8 bit serial data to control the relays would be the easy part.

Les.
 

MisterBill2

Joined Jan 23, 2018
4,846
Not only are power splitters expensive to buy, they also lose some power, and they work best with a good impedance match. So that is a second problem, because I am thinking that you will have 8 different antennas for 8 different frequency bands. so you may lose as much as 7/8 of the power that way. Not very efficient at all. And J hope that you have a license to transmit, they are required in much of the world. Please keep that in mind.
 
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