Re: QLG1 not seeing Sats

Alan de G1FXB

Hi Howard / Ron,

As the module has more than a fair opportunity to get lock by now....

Ignoring the No Green LED flashing,
and Just to rewind to earlier posts, one worry.

I see the changing voltages at TXD but nothing at the PPS output pins on the board.
I've done continuity checks from the PPS output pin back to IC1 (pin 3) , from the RF Module RF in ( pin 11) to ANT, also from RF Module PPS (pin 3) to IC1 (pin 1-2) all check good

Green LED tests good
Not sure what you mean by a "pulse"
With the scope on pin 1,2 and 3   I see a trigger flash on the scope but no voltage shows on the trace like  AND gate 9,10 (2.9V)   and 8 (5V)

Is this "trigger flash" regular & around 3v Or are you saying it's a random artefact triggering the scope?

PPS is a short duration 100mSec pulse
TXD is serial NMEA data, longer duration and 'easier' to see on a scope, or higher displayed voltage on a DVM.

Your QCX shows no indication at all, on the GPS menu ?
Previous from other owners but not known if 100% correct

With their findings of what's correct and not any other tips.
It would be REALLY useful shortcut to see if the NMEA string is all zero's or if it has parsed anything useful,
one way or another on a second known working device
It's going to upset the test equipment police....
Do you have anything to read TTL serial data?
do you have a $3 TTL / USB interface and windows terminal program.
Don't use Windows
Then a 'spare 'ardunio and a GPS sketch?

The reasoning behind why I previously suggested temporarily removing the cell....

   There is a circuit / data sheet discrepancy raised before.

(R8 & R9 look to be series charging current limiting resistors to the cell, R9 discharge limiting
Vbatt is only present on the full 6 way header pads, not on the 4 way that Hans describes as for U3 & later kits
that most will use as it removes the builder doubt of GPS TXD to connect to for instance U3's RXD)

I cannot find any instruction in the assembly manual to make a connection to apply external power to Vbatt header,
so charging voltage for the cell must come FROM the module?
(Somebody has observed a pulsing voltage on this pin on a previous thread.)

(If so, what is the purpose of R8 if it is in series to an unused pad?
It's not how other data sheets show it's use.
(Han's doesn't normally give us extras.   ))

    However the GPS kit has been on sale for long enough to know if the circuit simply didn't work by now.
The view in the past was to ignore the discrepancy as the Li cell will only back up the Sat data for a short period of time, and doing a cold start was not a great disadvantage.

(Ron, The image in the assembly manual of the cell, illustrates that the positive of the cell is the one with the 'L' shaped tab.)

Assuming the charging volts is supposed to be coming from the module, I suggested to temporary remove the cell so it didn't load the Vbatt pin of the module just in case....


On 15/02/2018 20:04, Ron Carr wrote:
In looking at the spec for the YIC module, about the only thing that would make it not work would be low voltage on Vbat.  You could measure that on the 6 pin header.  The spec says at least 2 volts.

When I built my kit, I found the polarity of the battery difficult to figure and had to use my meter to to find which connection was positive.  If your battery were in backwards, that would reduce the voltage on the Vbat pin.


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