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U2 Kit and Trimble GPS module advice required
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Andy Cutland
Last night I tried hooking up the gps module to the U2 kit. Nothing happened. I had 3v going to pin 7, earth at pin 9 and 3v via a 10k resistor on pin 8 which is the pull up to take the unit out of standby. I was intending to just use the pps output for frequency control and timing so that was connected to the relevant point on the U2 kit. The U2 refused to update the time so I thought something was wrong with my gps connections. I measured the voltage at pin 7 which showed 0.79v with a similar voltage showing on pin 8. Does this sound correct. I couldn't detect anything on the pps output pin (not sure what settings i need on the scope for this). I am going to take another look at it tonight with fresh eyes and a clearer head ! I am a complete newbie at this sort of thing so any advice would be most welcome. 73's Andy GJ7RWT |
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g3zjo
¿ªÔÆÌåÓýOn 29/05/2013 15:50, Andy Cutland wrote:Andy Something is wrong re pin7 showing? 0.79v. you have applied your 3v supply and here and you would expect to see that value, likewise with pin 8 the 10k should pull it up to the supply voltage. How have you derived your 3v supply. Is there a short somewhere in connecting up. Hopefully the GPS Module is not pulling down the supply. When you get the voltages right why not connect the Data also, this will update the clock to real time and is easily visible on a scope and the result is visible on the U2 nicely. The PPS out I could no see on my scope the only detection of its presence was by setting the scope to trigger on its leading edge. Bear in mind that the PPS needs a 3D lock and hence a good view of the satellites, the results on the U2 always come later than the real time update. 73 Eddie G3ZJO |
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Andy Cutland
Hi Eddie, I originally got my 3v from using a few diodes in series off the 5v reg pin. When this appeared not to work I then tried a pot but I may have limited the current too much with the output resistor so I need to experiment again tonight. I was really confused at this low voltage reading on pin 7. Will check again tonight and see what results I get. Thanks for the advice. 73's Andy From: g3zjo To: QRPLabs@... Sent: Wednesday, May 29, 2013 5:58 PM Subject: Re: [QRPLabs] U2 Kit and Trimble GPS module advice required
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On 29/05/2013 15:50, Andy Cutland wrote:
Andy Something is wrong re pin7 showing? 0.79v. you have applied your 3v supply and here and you would expect to see that value, likewise with pin 8 the 10k should pull it up to the supply voltage. How have you derived your 3v supply. Is there a short somewhere in connecting up. Hopefully the GPS Module is not pulling down the supply. When you get the voltages right why not connect the Data also, this will update the clock to real time and is easily visible on a scope and the result is visible on the U2 nicely. The PPS out I could no see on my scope the only detection of its presence was by setting the scope to trigger on its leading edge. Bear in mind that the PPS needs a 3D lock and hence a good view of the satellites, the results on the U2 always come later than the real time update. 73 Eddie G3ZJO |
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"andyfoad@..."
As Eddie says, I'd use a decent regulator rather than a zener.
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Also what are you measuring the 1pps signal with ? A DMM might not have the response time to show it properly, especially if it's a very narrow width pulse. An analogue meter would help, but a scope is better. Or, just to test it, an LED and a 1K resistor and it should pulse. 73 de Andy FTD --- In QRPLabs@..., Andy Cutland <gj7rwt@...> wrote:
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Andy Cutland
Thanks to all who sent advice. I am ordering some 3.3 regs today. Didn't get any shack tine last night so I have nothing to report back tight now. Will let you know how I get on.
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73's Andy ------------------------------ On Wed, May 29, 2013 10:29 AM PDT andyfoad@... wrote:
As Eddie says, I'd use a decent regulator rather than a zener. |
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