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Forum Index : Microcontroller and PC projects : Time$ very inaccurate
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BobD Guru  Joined: 07/12/2011 Location: AustraliaPosts: 935 |
One of my PCs outputs 5.1 volts on usb. I found that was high enough to stop some of my ds3231s from working. I put a diode in the supply and they worked again. They were sourced from China. |
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| viscomjim Guru Joined: 08/01/2014 Location: United StatesPosts: 925 |
If you would consider the GPS for setting your clock, another thing you could consider is the <$5.00 ESP8266 wifi module (of course if you have wifi available). You can grab the time from a server like yahoo, or others and set the uMite clock to that every once in a while. Just a thought.... |
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| hitsware Guru Joined: 23/11/2012 Location: United StatesPosts: 535 |
http://ww1.microchip.com/downloads/en/DeviceDoc/31002a.pdf FWIW  |
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| WhiteWizzard Guru Joined: 05/04/2013 Location: United KingdomPosts: 2932 |
I would only do this if the project was needing to use an 'internet' connection - the reason being these modules are reportedly using LOTS of power (over 500mA!) 
Good GPS units will draw below 50mA (while searching) and then much lower still to still be able to receive the time data. And if the unit is stationary (i.e. not moving GPS satellite fix location) then you can continue to run the GPS unit at a matter of just a few mA's for dead accurate (and auto updating) time. I can't comment about how much current the 'cheap' GPSs pull so this is an unknown as to whether it is viable to keep one of those running like I do with my uBlox modules. If anyone can do a test that would be useful info for others to have . . . . . |
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| edu001 Regular Member  Joined: 14/07/2014 Location: United KingdomPosts: 82 |
I only ever use genuine GPS modules for airborne tracking, I need the reliability and accuracy, the uBlox Max7 has a vast amount of config settings. As WW said it has very low power consumption if set up correctly, in power save mode with a 1Hz update it pulls about 6ma |
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| viscomjim Guru Joined: 08/01/2014 Location: United StatesPosts: 925 |
Hi White, you are absolutely right, these esp units are POWER HOGS! Not recommended for portable use. They are fun though. I need to get my hands on my first gps and give it a whirl. Does the unit you are using work well indoors or do you have to use an external antenna? Do you recommend one over another? Any input for a first timer would be appreciated. P.S. did you ever get the 8x8 matrix led scrolling thing working? Thanks!!! |
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| WhiteWizzard Guru Joined: 05/04/2013 Location: United KingdomPosts: 2932 |
@viscomjim uBlox Max7 (or the newer model 8) are my preferred choice of GPS module for two main reasons: 1> they work well indoors with an active antenna (chip antenna would need locating next to a window so I use the active antenna every time indoors) 2> as edu001 says, they pull next to no power for receiving GPS data i.e. below 10mA Price of these high quality units are about £30 + about £10 for an active antenna. I am going to be adding these to the website very soon - I do have some in stock (PM me if you want to get one rather than wait for me to add to website!) LED scrolling clock is beside my desk and remains unfinished - but I do know the EXACT time now 24/7 (other MicroMite commitments keep me from finishing the 'scrolling features') 
WW |
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