[GreenKeys] Current Loop to RS-232 Conversion on ASR33
Rob Jarratt
robert.jarratt at ntlworld.com
Mon Mar 25 18:40:26 EDT 2013
What I have tried is to configure the current loop side of the converter
into a loopback. When I do this the characters sent from the computer are
echoed back. I am using a terminal emulator to do this. Furthermore, when I
send a Break I see the current drop to zero (when the transmit side of the
converter is configured to be active - ie provide current).
So it would seem that the converter is working.
Regards
Rob
> -----Original Message-----
> From: greenkeys-bounces at mailman.qth.net [mailto:greenkeys-
> bounces at mailman.qth.net] On Behalf Of Simon Claessen
> Sent: 25 March 2013 12:16
> To: greenkeys at mailman.qth.net
> Subject: Re: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
>
> did you try to connect just a bulb or led to the output terminals of your
> converter to see if anything comes out at all?
> a led shoud have a series and parallel resistor to limit its current to
10mA
> max at about 2 volts.you shoud be able to see if blinking very rapid when
> sending repeatedly some carracters like ryryry
>
> simon
>
> On 24-03-13 18:25, Rob Jarratt wrote:
> > I have some additional information which may help to resolve this.
> >
> > I tried connecting my digital multimeter into the transmit circuit
> > while the current loop converter is connected to the Teletype. While
> > the Teletype is switched off or in Local mode I can see 20mA going
> > through the multimeter. When I switch it to Online mode the current
> jumps to 47mA.
> >
> > This made me think that perhaps the Teletype is providing the current,
> > even though I thought it wasn't supposed to. So I tried configuring
> > the current loop converter to be in passive mode on the transmit
circuit.
> > When I did this and switched the Teletype to Online mode, it did not
> > immediately start to chatter (run open), but I saw only about 10mA
> > flowing. After a short time though the current dropped somewhat and it
> > started to chatter again.
> >
> > When I tried sending a Break from the computer to the Teletype the
> > current did not change.
> >
> > Does this offer any different clues now?
> >
> > Thanks
> >
> > Rob
> >
> > *From:*greenkeys-bounces at mailman.qth.net
> > [mailto:greenkeys-bounces at mailman.qth.net] *On Behalf Of *Rob Jarratt
> > *Sent:* 16 March 2013 20:19
> > *To:* 'Alf Fisher'; 'Teletypeparts'; greenkeys at mailman.qth.net
> > *Subject:* Re: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
> >
> > It has been a little while since I looked at my ASR33 problem. Just to
> > refresh everyone: In Online mode I can send characters from the ASR33
> > to the computer, but the characters coming back do not print. It works
> > perfectly in Local mode. I have checked and it is full duplex 20ma,
> > which matches the setup of my current loop converter and I am using
> > 110bps, 7 data bits, 2 stop bits and Even parity. The ASR33 does not
> > chatter (run open) when connected to the converter.
> >
> > Today I tried sending a break from the PC to the Teletype. It did not
> > chatter when I sent the break. I verified with a multimeter that the
> > current goes to zero, so I am definitely sending the break.
> >
> > Does this offer any clues?
> >
> > Regards
> >
> > Rob
> >
> > *From:*Alf Fisher [mailto:alf_fisher at tiscali.co.uk]
> > *Sent:* 24 February 2013 21:39
> > *To:* r.jarratt at computer.org <mailto:r.jarratt at computer.org>;
> > 'Teletypeparts'; greenkeys at mailman.qth.net
> > <mailto:greenkeys at mailman.qth.net>
> > *Subject:* Re: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
> >
> > Hi Rob,
> >
> > I'm sure others will agree but I believe the ASR33 doesn't actually
> > need a high voltage source as there is a transistor circuit that
> > actually drives the electromagnet. I reckon 20 volts with a resistor
> > to limit the current to 20 mA should work.
> >
> > Is it possible with the Westermo, to loop-back the TTY to itself so
> > you can print what you type? I don't know what is in the converter but
> > another way may be to bridge the Tx & Rx pins on the Westermo RS232
> port
> > (pins 2 & 3?). It should work the same as being in Local but you
> > are switched to Line.
> >
> > Alf
> >
> > ----- Original Message -----
> >
> > *From:*Rob Jarratt <mailto:robert.jarratt at ntlworld.com>
> >
> > *To:*r.jarratt at computer.org <mailto:r.jarratt at computer.org> ;
> > 'Teletypeparts' <mailto:teletypeparts at aol.com> ;
> > greenkeys at mailman.qth.net <mailto:greenkeys at mailman.qth.net>
> >
> > *Sent:*Sunday, February 24, 2013 11:55 AM
> >
> > *Subject:*Re: [GreenKeys] Current Loop to RS-232 Conversion on
> > ASR33
> >
> > I have not looked at this problem for a week or so but will be
> > looking again today. To summarise, I can send characters from the
> > Teletype to my computer successfully, but any characters I send from
> > the computer to the Teletype do not print out.
> >
> > So far I have verified that the ASR33 is wired for 20ma Full Duplex
> > and that my Westermo converter works, because I can connect up the
> > current loop interface into a loopback configuration and I get the
> > characters I send on the RS232 side echoed back. I am using my RS232
> > port set at 110bits/sec, 7 data bits, 2 stop bits and even parity.
> > The battery test suggested by Teletypeparts has not worked though.
> > The only things I have yet to check are:
> >
> > 1.Is the mode relay inside the CCU is operating correctly? I used a
> > multi-meter to test that the contacts were made and broken
> > correctly. It looks to be making and breaking contacts OK for the
> > most part. One of the contacts (AM-15) seems a little bent,
> > requiring the relay to close completely to break the contact. As the
> > bend was such that the contact might not open correctly, I tried
> > isolating it with some paper, but it didn't seem to make any
> > difference. A couple of contact pairs showed shorts regardless of
> > the relay position, but the relay was fully wired in, so this might
> > be expected. The constantly shorted pairs are AM-9 with AM-8, and
> > AM-1 and AM-2. Is there a simple way to test the relay with a
> > battery? I am not sure what voltage and current it would need.
> >
> > 2.The voltage provided by the converter. I am told it needs to be
> > 80V and some converters do rather less, perhaps 20V. I have a
> > multi-meter, but in this case I am not sure where to measure the
> > voltage, I have tried T+ and T- with respect to the converter's
> > Shield connection and with respect to the TTY's earth but I don't
> > get any more than about 1 volt, this is whether I am sending
> > characters or not.
> >
> > Any ideas?
> >
> > Regards
> >
> > Rob
> >
> > *From:*greenkeys-bounces at mailman.qth.net
> > <mailto:greenkeys-bounces at mailman.qth.net>
> > [mailto:greenkeys-bounces at mailman.qth.net] *On Behalf Of *Rob
> Jarratt
> > *Sent:* 10 February 2013 23:10
> > *To:* 'Teletypeparts'; greenkeys at mailman.qth.net
> > <mailto:greenkeys at mailman.qth.net>
> > *Subject:* Re: [GreenKeys] Current Loop to RS-232 Conversion on
> > ASR33
> >
> > I tried a loopback test on my Westermo converter and that worked
> > fine when looping back from PC back to PC through the current loop.
> > I tried looping back from the TTY side via the RS232 interface and
> > there was no echo.
> >
> > I then tried the battery test you mentioned and unfortunately that
> > failed to work too.
> >
> > I think the problem must be inside the 33. L
> >
> > Regards
> >
> > Rob
> >
> > *From:*Teletypeparts [mailto:teletypeparts at aol.com]
> > *Sent:* 10 February 2013 22:28
> > *To:* r.jarratt at computer.org <mailto:r.jarratt at computer.org>;
> > greenkeys at mailman.qth.net <mailto:greenkeys at mailman.qth.net>
> > *Subject:* Re: [GreenKeys] Current Loop to RS-232 Conversion on
> > ASR33
> >
> > Rob,
> >
> > I have heard of the interfaces being bad but I am afraid I have
> > exhausted my limited knowledge of interfacing. Some of the guys on
> > Greenkeys may be able to help you.
> >
> > If you want to eliminate the 33 as a problem completely do the
> > following:
> >
> > Short together 4 and 6 and apply a 9 volt batt to 3 and 7. Again,
> > if it runs open reverse polarity on 3 and 7. Do the test in Line
> > mode. After you have the 33 running closed, type a few characters.
> > If they print OK the trouble is not in the 33. I still dont
> > recommend leaving the batt on very long. A minute or so. It may
> > not harm anything, but just to be sure keep the time short.
> >
> > What you have done is make the 33 half duplex (2 wire) and tested it
> > in line mode. I do that all the time here to check out the 33 in
> > Line mode. I also use a test generator, but before I had that I
> > used the 9 volt batt test.
> >
> > Wayne
> >
> > -----Original Message-----
> > From: Rob Jarratt <robert.jarratt at ntlworld.com
> > <mailto:robert.jarratt at ntlworld.com>>
> > To: 'Teletypeparts' <teletypeparts at aol.com
> > <mailto:teletypeparts at aol.com>>; greenkeys
> > <greenkeys at mailman.qth.net <mailto:greenkeys at mailman.qth.net>>
> > Sent: Sun, Feb 10, 2013 4:28 pm
> > Subject: RE: [GreenKeys] Current Loop to RS-232 Conversion on
> > ASR33
> >
> > I do understand about the echo that is needed to get characters to
> > print in line mode. I am using a terminal emulator on the PC to
> > receive and display the characters I type on the ASR33, and I type
> > characters into the terminal emulator to send them to the ASR33 in
> > the hope they will be printed. The emulator successfully displays
> > the characters I type into the ASR33, but the ASR33 does not print
> > the characters I type into the emulator, despite the Westermo LEDs
> > showing activity which suggests it is receiving the characters from
> > the emulator and sending them on to the ASR33.
> >
> > I had to re-read about start bits because I had forgotten about
> > them. I think start bits are always present, so there is no setting
> > to control them. So basically, I think I am already using 1 start
> > bit, 7 data bits, one parity bit and 2 stop bits, but nothing is
> > getting printed. I am using a line speed of 110 bits/sec, which in
> > this case corresponds to 110 baud too.
> >
> > I suppose the Westermo converter could be faulty and not sending
> > data out to the ASR33. Unless anyone has any other suggestions I'll
> > try a loopback test on the converter to see if it is working.
> >
> > Regards
> >
> > Rob
> >
> > *From:*greenkeys-bounces at mailman.qth.net
> > <mailto:greenkeys-bounces at mailman.qth.net>
> > [mailto:greenkeys-bounces at mailman.qth.net
> > <mailto:greenkeys-bounces at mailman.qth.net?>] *On Behalf Of
> > *Teletypeparts
> > *Sent:* 10 February 2013 18:20
> > *To:* r.jarratt at computer.org <mailto:r.jarratt at computer.org>;
> > greenkeys at mailman.qth.net <mailto:greenkeys at mailman.qth.net>
> > *Subject:* Re: [GreenKeys] Current Loop to RS-232 Conversion on
> > ASR33
> >
> > Rob,
> >
> > Read on as I put something important below.
> >
> > I guess the voltage doesnt need to be 80 or more. It may run OK
> > with less. The norm is 20 MA at 120 VDC.
> >
> > I dont know anything about the Westermo, but I know that when you
> > send to the computer from the 33 the computer needs to be
> programmed
> > to echo back to get a copy on the 33.
> >
> > When you type in Local, the print is pretty much instant. When you
> > type in Line thru the computer you will see a slight delay, not much
> > but enough to notice.
> >
> > The 33 doesnt care about parity on its receive side, it will print
> > whatever the bits from 1 to 7 are. The 33 is 110 baud, not sure
> > what that converts to in computer language.
> >
> > Oh and this is important, you need a START bit which is always a
> > zero or a space or no current which all terms seem to be
> > interchangeable. The rest you got correct. Its one start bit, 7
> > data bits, one parity bit and 2 stop bits. The 33 will run with 1
> > stop bit, but its normal to give it two when you can.
> >
> > If you put the START bit in, I bet it will work.
> >
> > Wayne
> >
> > -----Original Message-----
> > From: Rob Jarratt <robert.jarratt at ntlworld.com
> > <mailto:robert.jarratt at ntlworld.com>>
> > To: 'Teletypeparts' <teletypeparts at aol.com
> > <mailto:teletypeparts at aol.com>>; greenkeys
> > <greenkeys at mailman.qth.net <mailto:greenkeys at mailman.qth.net>>
> > Sent: Sun, Feb 10, 2013 5:36 am
> > Subject: RE: [GreenKeys] Current Loop to RS-232 Conversion on
> > ASR33
> >
> > I made some great progress, with one last hurdle to overcome.
> >
> > I configured the Westermo to be in active mode (ie supply current)
> > on both its receive and transmit sides). This cured the problem with
> > the RD light on the Westermo being on all the time and it stopped
> > the chattering too.
> >
> > I connected it up to a terminal emulator running on my PC. When I
> > press a key on the ASR33 the corresponding character appears on the
> > terminal emulator. However, when I try to send characters from the
> > terminal emulator to the ASR33 nothing happens. I am using 110bps, 7
> > data bits, even parity and 2 stop bits.
> >
> > As the chattering has stopped, does this mean that the Westermo's
> > transmit side is set up correctly now?
> >
> > Am I using the right serial port settings?
> >
> > Could the Westermo not be outputting the right voltage? It is a 20ma
> > interface, but the manual does not say anything about the voltage
> > which you say needs to be 80V or more.
> >
> > What else might prevent the characters from being printed out?
> >
> > Regards
> >
> > Rob
> >
> > *From:*Teletypeparts [mailto:teletypeparts at aol.com
> > <mailto:teletypeparts at aol.com?>]
> > *Sent:* 09 February 2013 20:30
> > *To:* r.jarratt at computer.org <mailto:r.jarratt at computer.org>;
> > greenkeys at mailman.qth.net <mailto:greenkeys at mailman.qth.net>
> > *Subject:* Re: [GreenKeys] Current Loop to RS-232 Conversion on
> > ASR33
> >
> > Rob,
> >
> > The 33 should chatter or run open when in Line mode and not
> > connected to anything. The reading of a short is normal as on 3 and
> > 4 you are basically looking at a switch, the distributor of the 33.
> > Same reading on 6 and 7 as I recall.
> >
> > Neither side of the 33 generates any current. The receive wants 20
> > MA at 80 volts or more and the send will accept whatever the
> > interface gives it, usually 12 or 15 volts.
> >
> > A quick test you can do is wire a 9 volt batt to 6 and 7 while in
> > line mode. You have a 50/50 chance of getting the polarity
> > correct. If still running open, reverse the leads. The 33 should
> > run closed. Dont leave the batt connected for a long time. You
> > have now verified the 33 will run closed in Line mode and you need
> > to proceed with the adapter stuff of which I know very little.
> >
> > I believe the Send side of the Westmo should be set to active to
> > generate 20 MA current for 6 and 7 of the 33.
> >
> > Dont know about the Westmo receive side.
> >
> > Hope this helps,
> >
> > Wayne
> >
> > -----Original Message-----
> > From: Rob Jarratt <robert.jarratt at ntlworld.com
> > <mailto:robert.jarratt at ntlworld.com>>
> > To: greenkeys <greenkeys at mailman.qth.net
> > <mailto:greenkeys at mailman.qth.net>>
> > Sent: Sat, Feb 9, 2013 7:22 am
> > Subject: [GreenKeys] Current Loop to RS-232 Conversion on ASR33
> >
> > I emailed this list a little while ago about getting my ASR33 to
> > talk RS-232. I have since sourced a Westermo MA-21 current loop
> > converter.
> >
> > I have noticed however, that the ASR33 will "chatter" in line mode
> > regardless of whether the current loop wires are connected to
> > anything or not. When I plug it into the Westermo the RD light on
> > the Westermo comes on even if the ASR33 is disconnected from the
> > mains. The RD light is supposed to come on when it is receiving data
> > from the line interface (manual here if you want to see it:
> > http://www.westermosales.com/pdfs/MA-21manualENGSEDE.pdf),
> which
> > makes no sense if the ASR33 is not even connected to the mains.
> >
> > I have set both the receive and transmit side of the converter to
> > passive mode for now (ie they don't generate the current), but I
> > think the receive side of the converter will need to be set to be
> > active so that it generates the current because the drawings of the
> > ASR33 suggest that the ASR33 receive side generates current but the
> > transmit side does not. In fact all the switches are set to the
> > factory settings at the moment.
> >
> > I tried switching the receive side of the converter to active and
> > when I switched on the converter (with the ASR33 disconnected from
> > the mains) the RD light did not come on this time.
> >
> > I have also noticed that with the ASR33 disconnected from power the
> > screw terminal pairs 3&4 and 6&7 appear to be shorted (ie 3 shorted
> > to 4, 6 shorted to 7). I suspect this may be expected but I am not
sure.
> >
> > I have wired screw terminals 3&4 on the ASR33 to the Receiver side
> > of the Westemo, and 6&7 to the Transmitter side.
> >
> > I wonder if there is a fault in the ASR33, should it chatter in line
> > mode when it is not connected to anything?
> >
> > Which side (if any) of the Westermo should be set to active to
> > generate current?
> >
> > Regards
> >
> > Rob
> >
> >
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> Met vriendelijke Groet,
>
> Simon Claessen
> drukknop.nl
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