All of my Projects at the Naval Acadmy and our satellite designs, PSAT2
(on orbit) use the MTT4B basic system, but the first thing we do is remove
the MAX232 chip since its internal buck/boost converter to get
RS232 level generates too much RFI for use in a weak signal system.
We interface to other stuff at TTL levels. If used as a tracker, I;d
deflinately
pull the MAX232 chip after programming, though I guess if it is a tracker
only, then it does not need to hear weak signals anyway.
Oh, removing the MAX232 chip also saves about 8 mA which is very usefdul
on a cubesat.
CAVEAT! This is all from memory and could be erroneous.
Bob, WB4APR
On Sun, Oct 17, 2021 at 8:26 PM vhsproducts via groups.io
<vhsproducts@...> wrote:
Compton,
Why not reset the timer more often? (Every day?) Are you finding that once a week is enough to keep the units running reliably? Our problem is not being able to replicate the hanging complaint in a TT4 or an MTT4BT. I recently found that the MAX232 chip has a non-documented problem that occasionally causes the chip to lock up, overheat, and draw a bunch of excess power ( Google "MAX232 overheating" and you will see that the problem with the chip has been going on for years with no satisfactory explanation) I hoped I could find someone who has consistent lock-up to see if pulling the MAX232 chip solved the problem...of course, this would need to be in a digipeater or similar application where the serial ports are not in use during operation. When the MAX gets hot, it may start sending gibberish to the TT4 chip. I like your timer solution, but I wish it was not necessary! If you get to one of your remote units, can you see if pulling the MAX chip makes any difference?
73,
Allen
-----Original Message-----
From: Compton <comptonallen@...>
To: [email protected]
Sent: Sun, Oct 17, 2021 3:06 pm
Subject: Re: [TinyTrak] MT4BB Halting
[Edited Message Follows]
I am in a group in Sydney that uses 4 of these. We experence the same issue. We ended up fitting a timer that turns the power on/off. We set the time to do this every Tue at 2AM. If they happen to go off air during the week then the timer will revive them on Tues at 2AM. Yes, its an annnnoying porblem but the timer does work as a good work around. We are suspicious of RF getting into them that causes the hang up to occur. Seems to occur in the 2-3 month time period but we can see no pattern to it.
Allen and Byron at Byonics are aware of the issue.
This is the timer we use:
--
Compton
VK2HRX
Sydney, Australia
