Re: [tracker2] Questions about T3mini and GT-320FW GPS
- To answer a few of these questions:
Schematic can be found on the wiki:
I'm not familiar with your GPS, but the ADS-GM1 GPS blinks until it has a
RFI is always an issue in small installs with unshielded wires and
components. You can try out some bypass caps or a shielded enclosure.
Shielded twisted pair will always help as well as long as you ground the
shields too. The ferrite beads definitely will help. Be sure to test your
setup with the diagnostics window in OTWINCFG as well. Also check your H/T
Your 5V rail should read 5.0V +/- 5%. If it's not then you'll need to look
for some shorts or other issues. Maybe the GPS is drawing a lot? Does your
GPS use 5V in as well?
Hope this helps a bit,
On Jul 14, 2013 4:58 AM, "Will" <engineer1@...> wrote:
> Working on getting my Tracker going using the nwes T3mini and the GT-320FW
> GPS unit. Im having start-up problem with this setup and have a few
> Problems - Does the LED on the GPS when flashing mean it is not locked to
> the Sats? I put it out in the open for an hour and the LED never went solid
> on like other units I am using.
> Question: I do not see level converters on RX2/TX2 so I am using the TTL
> level signals from the GPS unit, correct?
> Problem - When testing with otwincfg.exe and I enable the PTT and the
> T3mini seems to crash, or gets stuck with TX on. Is it sensitive to RF like
> the TinyTracker3? I am using a UV-5R+ set to low power and have ferrite
> core on all leads runing to the T3mini. Is it possible to bypass the PTT
> transistor with caps?
> Problem - I am running the tracker package on 6 AA bats or about 9 volts
> and the 5volt VReg gets pretty warm with an output voltage of 4.6 not 5,
> and thats with the GPS disconnected, Im not sure where the load is coming
> from. Suggestions?
> Have you published a Schematic somewhere for the T3Mini. What is on the
> web site looks to be for the OT3m.
> Sorry for all the questions, but I know it is a new product and there is
> not much information on the web for it yet.
> Thanks for the help -
> Will - N7IPY
Thanks for the message.
Yesterday I went back and rewired the tracker I am assembling. I removed any extra lengths of wire and adding an additional amount of ferrite cores. That removed enough RF from the system to keep the T3-Mini from going nuts when the HT is at 4Watts, all fitting inside of a little Pelican 1030 case.
Also, thanks to the wiki reference, I missed it when looking for information. The higher than expected power draw occurs even when just the T3-Mini is attached to the batteries, no GPS connected. 9-12 volts is a lot to send into a little linear regulator, so Ill add a small current limiting resistor in series to see if that helps to reduce current draw. I still do not understand the lower than expected 4.5 vs 5.0 out of the 78L05. I'll try adding a bit more filter capacitance; .1uf on the output is pretty small. Now that I have the actual schematic, I can do more troubleshooting.
I also found the proper reference to the GPS unit. Looks like it flashes it's LED On/Off at a 1 sec per state rate. The data it is sending out is garbage though it looks to be structured in format suggesting I have something set wrong or the data that is being sent is KISS formatted. I am using putty to keyboard control the T3-Mini via USB, entering the 'SNOOP' command, GPS is on port B.
By the way, does anyone know haw the 'HT-PTT' switch in OpenTracker Configuration correlates to the 'HT' Solder Pads on the tracker?
More to follow as I learn more.
Will - N7IPY
- An update -
Well Silly me, the voltage drop seen at the 5V pin is caused by the isolation diode D2 dropping about .45 volts. The regulator output is spot on 5 Volts prior to the diode.
The tracker and GPS are drawing 90ma at 8.9 volts which seems high. There is still a lot of heat generated at U1 the voltage regulator. To reduce the power loss, I think the only solution would be to remove U1 and replace the circuit with a VR that is better suited for higher input voltages, something like a LK112SM50.
I am still unable to get the GPS unit to send usable data on the TTL Out line.
I hate to say it, but I think I will need to scrap this hardware and replace it with the other companies SMT tracker. The feature set of the T3-Mini are awesome, but the power draw is too great and the GPS... well I don't think I know what to say about it.. I know the other set up works as my first tracker was based on it and it works fine, just a little more expensize.
Will - N7IPY
A few comments:
- You should be using the RS232 output on the GPS for the argent products.
See: https://www.argentdata.com/catalog/product_info.php?products_id=144 Be
sure to use the correct cable pinouts from the GPS and try again. Hopefully
that will solve the GPS part of the problem.
- The currents you are reporting seem to be ballpark ok. The OT3m normally
draws 40mA (so I presume the mini is in the same range (I don't have one
here to check)). The GPS will draw <45mA (
http://www.argentdata.com/files/GT-320FW.pdf) so the 90mA you are reporting
doesn't seem far off from what you would expect. Keep in mind the 78L05UA
regulator in use maxes out at 100mA, so if you're measuring the 90mA on the
input, then there is a good chance it's being overdriven. You might want to
check the GPS current inline and double check your wiring in case something
is shorting and causing the regulator to max out. That regulator is
designed to handle the tracker plus a GPS puck.
I hope this helps out a bit. Keep us posted with your progress!
On Tue, Jul 16, 2013 at 7:39 AM, Will <engineer1@...> wrote:
> An update -
> Well Silly me, the voltage drop seen at the 5V pin is caused by the
> isolation diode D2 dropping about .45 volts. The regulator output is spot
> on 5 Volts prior to the diode.
> The tracker and GPS are drawing 90ma at 8.9 volts which seems high. There
> is still a lot of heat generated at U1 the voltage regulator. To reduce the
> power loss, I think the only solution would be to remove U1 and replace the
> circuit with a VR that is better suited for higher input voltages,
> something like a LK112SM50.
> I am still unable to get the GPS unit to send usable data on the TTL Out
> I hate to say it, but I think I will need to scrap this hardware and
> replace it with the other companies SMT tracker. The feature set of the
> T3-Mini are awesome, but the power draw is too great and the GPS... well I
> don't think I know what to say about it.. I know the other set up works as
> my first tracker was based on it and it works fine, just a little more
> Will - N7IPY