What is the cheapest way to get a GPS + solid state gyro?

I am looking at a project which requires a simple GPS receiver (not waas/egnos) and a low grade solid state gyro (not a "level") like the ones you get in smartphones.

The build volumes will be initially a batch of 100 and later perhaps thousands, but not more than that.

What would be the currently recommended GPS module or chip, and a solid state gyro component?

There is a lot of stuff on the market...

One requirement is reasonably low power - milliamps rather than 10s of milliamps. I have no idea if that is possible.

Ideally the two items can be obtained for under $20-30.

Any pointers would be much appreciated.

Reply to
Peter
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I'd start by checking DigiKey and Mouser for the gyro chips, and maybe Circuit Cellar ads for GPS modules (as well as DigiKey).

There's not a lot of GPS augmentation that you can do with a gyro and no accelerometer -- what are you trying to do?

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Tim Wescott
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Reply to
Tim Wescott

Most of the chips are already three axis, so don't get high hopes of finding cheap solutions for two axis, when the rest of the world made three axis parts cheap for you already.

Reply to
Chieftain of the Carpet Crawlers

I have not yet found a GPS solution that can give 1HZ updates and draw less than about 20mA. There are some that can go into a low-power sleep mode and wake up on command to give a fix. However, when awake, they still draw 20 to 30mA. To get the overall power down, you need a fairly low duty cycle.

The low end for GPS chips that I've used is about $30 qty 1.

Mark Borgerson

Reply to
Mark Borgerson

GPS module + chip antenna should be around $17 quantity one.

Cost of gyros and translational accelerometers depends a lot on their performance, from a few dollars up to serious dollars/euros for military grade stuff.

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

Which module would that be? A few years ago I used a now-discontinued Delorme module that was about $35 qty 1. I couldn't find anything in stock at DigiKey in the $17 price range.

Mark Borgerson

Reply to
Mark Borgerson

GlobalSat or U-blox modules with SiRF III etc. are around $15 shipped.

Eg.

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Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

The GPSs in cars (built in units) have accelerometers. It makes the user experience better since it can sense a turn before differential waypoints can sense it. I don't think they have to be very good to do that task.

They can also do dead reckoning fairly well, but I've never been out of GPS contact for more than a few miles.

There is a usenet group on gps.

Reply to
miso

I noticed when driving a new car in Europe that the nav system managed to track fairly well through long tunnels. Makes sense that they would stick an accelerometer and/or gyros in there for when the GNSS satellite signal is not available- tunnels and urban driving between tall buildings. Even a lousy MEMS gyro won't drift that many degrees in a few minutes.

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

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Thanks for the lead. I used U-Blox modules about 6 years ago in an autonomous flight controller when they were one of the few manufacturers offering 5Hz update rates at reasonble prices (about $100 then).

I haven't tried the Gloalsat modules before. Definitely worth investigating for a project that's been on the back burner for a while.

Mark Borgerson

Reply to
Mark Borgerson

I'm nearly 100% sure that if you want to do credible dead reckoning you need accelerometers and gyros, not just one or the other. Gyros don't mean much when you don't know the acceleration, and accelerometers don't mean much when you don't know the vehicle direction.

If there's no skidding going on, a good odometer and a steering position sensor may work better than an IMU, though.

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Tim Wescott
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Reply to
Tim Wescott

On a sunny day (Mon, 30 Apr 2012 00:07:14 -0400) it happened Spehro Pefhany wrote in :

Do those modules come with any sort of datasheet?

Reply to
Jan Panteltje

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Why can't you figure out the direction with 2D accelerometers?

Reply to
linnix

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Google found this:

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Reply to
hamilton

All six degrees of freedom, three rotation and three translation, are required for a general-purpose INS. *But* if you're able to constrain the problem to, say, non-skidding/slipping car behavior then yes, two properly mounted orthogonal accelerometers could do a pretty reasonable job, modulo the usual caveats of noise and sensor drift, given an initial (or periodic) knowledge of heading and position. Better if you also include the vehicle speed in the mix, of course.

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Rich Webb     Norfolk, VA
Reply to
Rich Webb

Check the manufacturer website, I doubt DX will give yo anything more than a padded envelope marked "gift".

Reply to
Spehro Pefhany

Because without a gyro or some other angular reference you don't know what direction they're pointed.

I suppose that if you were really cost-conscious you could assume no skidding and take sideways acceleration to be an indication of turning rate -- but that's a pretty tenuous connection to reality.

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Reply to
Tim Wescott

How about a compass module for orientation? That'll probably work OK for 2D navigation tasks between GPS fixes. Not sure what the OP needs.

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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Reply to
Paul Hovnanian P.E.

On a sunny day (Mon, 30 Apr 2012 16:31:37 -0400) it happened Spehro Pefhany wrote in :

OK The FM modules for Hongong I have, at least had a pin connection diagram...

Reply to
Jan Panteltje

On a sunny day (Mon, 30 Apr 2012 13:36:14 -0600) it happened hamilton wrote in :

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Thanks! I have downloaded the pdfs, maybe I buy one just for fun, could be an other PIC project, and combine with my fluxgate compass... Years of fun ahaead... Maybe needs a more powerful computah, one of those recent Linux based boards perhapds (display maps on LCD etc). ;-) I would not use FAT filesystem ....

Reply to
Jan Panteltje

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