[time-nuts] Z3805 utility, Was: AW: (no subject)

Bob Camp lists at rtty.us
Sun May 23 02:54:50 UTC 2010


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 <didier at cox.net> 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 <bruce.griffiths at xtra.co.nz>
>> Date: Sun, 23 May 2010 10:39:21
>> To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
>> 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: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] 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: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] 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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>> 
>> 
>> 
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