Thank you all for these inputs!
Most importantly, the big question is: Regardless of RS-232 or 422, will the unit do ANYTHING without communications?
Do I need a computer to get anything beyond the "power" led?
I bought this at the Dayton convention ham flea market, and the guy told me it was already modified for RS-232. The
board inside says RS-422 near the connector. Without the other LEDs blinking, I'm worried I bought a dead unit. I had
a GPS antenna on it, but it never locked on. Do I need a computer to enable this thing?
Thanks,
Bob
----- Original Message -----
From: "Bob Camp" <[email protected]>
To: "Discussion of precise time and frequency measurement" <[email protected]>
Sent: Saturday, May 22, 2010 10:54 PM
Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
Hi
In this case the RS relates to Radio Shack ......
Not a lot of standardization in the RS-232 world. Take a look at the slew rate limiting requirements in the original
document ...
Bob
On May 22, 2010, at 9:47 PM, Robert Darlington wrote:
Was there ever a standard? I always thought the "RS" stood for
Recommended Standard, as in "you *should* do the following" as
compared to "you shall do the following" I've seen inverted TTL talk
to the RS232 port on laptops and I even sometimes use the max233's
(+/- 10 volts instead of 12), but always use the full max232 with
external charge pumps when it's a gadget that needs to work everytime
with systems from multiple countries.
-Bob
On Sat, May 22, 2010 at 7:21 PM, Didier Juges <[email protected]> wrote:
Bruce,
Thanks for the additional information.
+/- 14V is quite unusually low in my experience. I typically use Maxim parts such as the MAX220 series, which is
specified at +/-25V for no damage on the inputs (some parts in that series go to +/-30V).
The bottom line is that as I pointed out earlier, there is no such thing as an
RS-232 standard any more.
Didier
------------------------ Sent from my BlackBerry Wireless thingy while I do
other things...
-----Original Message-----
From: Bruce Griffiths <[email protected]>
Date: Sun, 23 May 2010 10:39:21
To: Discussion of precise time and frequency measurement<[email protected]>
Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
Didier Juges wrote:
Bill, I think you got it backwards. +/- 12V is typical for RS-232, 0/+5V is
for RS-422 and RS-485.
No RS-232 receiver should be damaged with +/- 12V or even +/- 15V because
that is their normal operating voltage.
Also, RS-422 and RS-485 have something like 25V common mode tolerance (not
sure what the actual spec is there,) so that the RS-422 and RS-485 receivers
should not be damaged by 15V either. The RS-422 drivers are pretty low
impedance, while the RS-232 drivers are current limited, so I don't think
that connecting an RS-232 driver into an RS-422 driver will damage either.
Picking one RS485 receiver (ADM1485) at random the receiver absolute
maximum (no damage) input range is -14V to +14V.
The RS485 receiver operating common mode range is -7V to +12V.
RS422 receivers have an input operating range of -7V to +7V.
The no damage RS422 receiver input ratings may be higher.
However, most recent (<10 years?) RS-232 receivers will work with a 0/+3V or
0/+5V input, conveniently having a threshold a few 10's or 100's of mV above
ground, even though the original RS-232 spec required receivers that work
with as low as +/- 3V, and drivers that deliver +/- 9V minimum. Many
commercial systems use +/- 5V drivers for RS-232 (B&B Electronics sells a
lot of converters with these voltages). This is a deliciously sloppy spec
that nobody has met in the last 25 years probably, yet works most of the
time.
The one thing to avoid is to short an RS-422 (or RS-485) driver to ground,
as that can actually cause damage, maybe not every time, but definitely not
recommended. These have relatively high current output capability to drive
long lines.
Didier KO4BB
Bruce
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Bill Hawkins
Sent: Saturday, May 22, 2010 3:09 PM
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
When all else fails, get out the voltmeter.
Do you have power to the antenna? Is it the right voltage? All the way to
the antenna?
What volts are on pins 2 or 3 relative to pin 7 in the comm connector?
If you see 12 volts, that's RS-422. You may have burned out your computer's
serial port.
If you see less than 5 volts, that's RS-232 and all should be well, unless
you see zero volts.
I may have the RS-xxx volts somewhat off because my memory isn't what it
used to be.
The guy you bought it from should be able to help with comm basics.
Bill Hawkins
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Robert Benward
Sent: Saturday, May 22, 2010 2:08 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject)
Hi All,
I hooked everything up and I still get nothing. I can't seem to establish
communications with the Z3805. I tried a
null modem as well, in case the cable (supplied) was wired with the wrong
connector gender. I see a green blinking
light inside, it he left rear corner of the box. Everything is warm, but
nothing else. Any ideas?
Bob
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