Hello Gentlemen,

I'm looking for a way to have 10 devices connected to the same serial port, while only having one transmit/be powered at any one time. Essentially, I'm looking at having a switch box for the power supply but some way to have multiple rs232 connections that don't have to be manually switched at the same time as the power supply switch box (although i'm open to that as well).

Ive seen a lot of devices where one transmitter can be connected to multiple receivers but not the other way around.

Thanks in advance

 

hi g,
Welcome to AAC.
Do you want full duplex comms on the selected 1 of 10 incoming transmitter.?
E

 

Thanks for the quick reply. Yes I do

 

Hello Gentlemen,

I'm looking for a way to have 10 devices connected to the same serial port, while only having one transmit/be powered at any one time. Essentially, I'm looking at having a switch box for the power supply but some way to have multiple rs232 connections that don't have to be manually switched at the same time as the power supply switch box (although i'm open to that as well).

Ive seen a lot of devices where one transmitter can be connected to multiple receivers but not the other way around.

Thanks in advance

Do you know what the characteristics of the un-powered transmitters will do to the transmitter that is powered? The complexity of this scheme makes it unlikely you will ever receive any benefit from doing this. Just use RS-485 an the comms problem is solved

 

@papa So convert from rs232 on each end and have multiple receivers on the rs485 line to the receiver port?

 

hi,
If I understand your app correctly.
You could use low power reed/coil relays that select the desired incoming RXDin line.
Power the selected reed-coil from the power select switch.
Likewise for the outgoing TXDout line.
There are various DIP style reed relays.
E

 

Do you know what the characteristics of the un-powered transmitters will do to the transmitter that is powered? The complexity of this scheme makes it unlikely you will ever receive any benefit from doing this. Just use RS-485 an the comms problem is solved

Doing some research, it appears rs485 is for one way communication?

 

hi,
If I understand your app correctly.
You could use low power reed/coil relays that select the desired incoming RXDin line.
Power the selected reed-coil from the power select switch.
Likewise for the outgoing TXDout line.
There are various DIP style reed relays.
E

By switching the RXD line and outgoing TXDout line using reed relays would I would be able to avoid converting to 422?

 

hi,
What length are the RS232 cables from the Master to Slaves.?
E

 

1-3 feet

 

hi,
No problem, upto 100ft is possible with RS232, using the correct cabling.
E

EDIT:
Wire the PC 9Way serial input connector as a null modem, so the PC will not require any handshaking, you can then use Half Duplex. ie two way comms.

 

Doing some research, it appears rs485 is for one way communication?

That is wrong. It is two way multi-drop half duplex for a 2-wire system. Full duplex for a 4-wire system. Where do you get your information?

 

That is wrong. It is two way multi-drop half duplex for a 2-wire system. Full duplex for a 4-wire system. Where do you get your information?

looked at 2 wire systems i suppose. So I can use 4 wire duplex 485 for my purposes?

 

looked at 2 wire systems i suppose. So I can use 4 wire duplex 485 for my purposes?

You can use either one.
Full duplex meas you can transmit and receive at the same time.
Half duplex means you transmit and then you listen, or you listen and then transmit, but you don't do both at the same time.

 

You can use either one.
Full duplex meas you can transmit and receive at the same time.
Half duplex means you transmit and then you listen, or you listen and then transmit, but you don't do both at the same time.

that's what i meant by one way communication, and i do want duplex. Thanks for your help

 

Simple question first:
> Do you have control over the comm protocol?
If so, make each unit addressable
> Else, I'd use a set of 1488s to select the TTL Tx output stream.
3 of the 4 are NAND gated. Since you select, you'll know who's responding.
> Shouldn't be too hard to wire-OR the Rx streams.
This presumes a poll / respond to each selectable unit.