[GreenKeys] Current Loop to RS-232 Conversion on ASR33
Simon Claessen
simski at dds.nl
Mon Mar 25 08:15:47 EDT 2013
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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