How to assemble an SMD GPS Device - OHARARP LLC

SD GPS Data Logger - www.ohararp.com/products

I am a small developer of embedded soultions for all types of applications. One my personal interests is with GPS positioning products. To satisfy some previous patent work I was doing I needed a device that would record large amounts of gps data (lots of memory) over a long period of time (big battery) and was compatible with mac's and pc's. Unfortunately, nothing of this sort existed and I had to create a device to do this.

This product is the culmination of implementing a number of new designs for myself. Mainly, using surface mount components, lithium ion/polymer batteries, and Sandisk SD memory cards.

Since so many electronics parts are surface mount these days I needed to use these components but was a little bit fearful in making the leap from using through hole/traditional soldered parts. Sparkfun Electronics helped my learning with their tutorials and I thought I would continue the tradition through an Instructable.

Step 1 APPLY SOLDER PASTE WITH ACRYLIC STENCIL

Picture 1. Place circuit board where it can be held securely
Picture 2. Tape Top of acrylic stencil to board; make sure it is properly aligned over the pads of your pcb.
Picture 3. Using your preferred solder paste apply a good sized glob to a simple plastic paint spreader
Picture 4. Spread the solder past liberally over your acrylic stencil. Make sure to cover all the holes!
Picture 5. In the next 2-3 passes try and remove as much solder paste from the stencil as possible.
Picture 6. You should have almost the same amount of solder paste your "spatula" as you began with except for the holes in the stencil.
Picture 7. After carefully pulling up your stencil and removing the pcb you would repeat this process for the next board. When complete be sure to remove all solder paste from the stencil. I prefer windex and a toothbrush to clear out soem of the holes for really tight pitch components.

Comments

[james.mcglashan]

does this have a screen extention ???

[ohararp]

james no screen on this device. Total passive logger.

[james.mcglashan]

ok pitty lol it should have 1 so u can use it as a gps.

[collard41]

$175!!! i bet the components only cost $50, mostly for the battery and the GPS module. do you think you could post a picture of the schematics. or something.and also, when you connect it to your computer, does it send coordinates, and speed and direction, or do you have to work them out yourself.i have to say, i agree with the people who say that this is geared to advertsing

[myozone]

Cheaper one's here ..
http://www.sparkfun.com/commerce/categories.php?cPath=4_86

[ohararp]

To bad the logger only logs for 8 hours. They are using a lot of power for their device. Not sure why. My design only requires ~58 mA and can run for ~48 hours continuously. We also implement a sleep mode that draws <1mA. Oh, and the product isn't available yet nor does it come with an SD Card.

[myozone]

Hello, yes indeed your's looks to be a better option, I was mearly pointing out that there are other options.

[Chavez]

(removed by author or community request)

[ohararp]

You wouldn't believe ow many e-mails I get about people being afraid of using smd components. Sparkfun posted something similar on their website to this instructable. It prompted me to go out and MAKE things. I wanted to address a couple of things in this instructable: 1. Show that normal people can make things using smd components. If you feel particularly interested you could even start a business. 2. If you are going to use li-ion batteries in your project you should always use a protection circuit module (pcm). 3. Finally, I wanted to show the whole process of pcb's, smt parts, enclosure, etc. A lot of instructables out there are "hacks" and that's great but not many people show how a product could be made applying just a bit more thought than say "fixing some headphones".

[johngomm]

Re-reading the article, I think the SMD process could do with a bit more detail. For example, the acrylic stencil you refer to is not clearly shown or described. How do you make the stencil? Are there tricks to ensuring the right amount of solder paste? Would you recommend this technique if you were doing small runs of <20 or is it better to hand solder, as I've seen other people do with SMDs? I like most of the introduction you have now, but Chavez does have a point that it does have a hint of an advert to it. Maybe if you sold a home-solder parts kit with circuit board, this might change the tone.

[ohararp]

John, Thanks for your constructive input! I took out the last part of the intro. Really, this is meant to be helpful. I will try and add a bit more info on the stencils. Being that they are thin clear acrylic they don't photograph well. Heck, I might just make a separate instructable on this process. I like your idea about the home solder kit too! Now that could be a helpful product that no one is really offering right now. If a kit like this were available what would you want it to do? I figure it would have to have some blinky lights for sure! Maybe a SMT POV project?

[Chavez]

(removed by author or community request)

[ohararp]

Chavez, I typically use matlab to sift through all the data and would be more than willing to share this code. The easier route is to upload the files to www.gpsvisualizer.com. This is the gpsbabel for the web! Its great for all types of formats.

[ohararp]

Hey all thanks for the input. I tried to make a few changes to help introduce everything. To help answer your questions John: 1. Price is $175 2. We considered an LCD but wanted to keep power draw as low as possible for maximum runtime. For instance, a # of customers use them for animal tracking over several months. 3. I prefer www.mouser.com for most of my parts...They have a great "projects" page that keeps track of all your parts for a particular project that is really helpful. 4. With the datasheet I include a schematic. Otherwise, I have released some previous source code, but like to keep that part for me. However, I do modify the firmware for customers, usually at no cost for their particular projects.

[johngomm]

How much would one of these cost? Would it be easy to add a read out lcd so one could know where you were in real time without attaching a PC? What's your favored source for components? Are your designs open for user modification? I agree with dchall8, it would be great to have that little explanation up front in your instructable, so people have their curiosity peaked before they wade in to technical surface mount details. Other than that, nice photos and pretty clear instructions. Good job.

[dchall8]

I'm starting to sound like a broken record. Please explain what you're talking about. Start by spelling out SD GPS. I think I know what GPS is, but maybe not. What does this do? Why or when or where would I want one? Why would I want to log it and what's smd?

[computer_gui]

Secure Digital (SD) is a flash (non-volatile) memory card format developed portable devices, including digital cameras, handheld computers, PDAs and GPS units.

The Global Positioning System (GPS) is a fully functional Global Navigation Satellite System. Satellites transmit signals that enables a GPS receiver to determine its location, speed and direction.

Surface mount technology (SMT) is a method for constructing electronic circuits in which the components are mounted directly onto the surface of printed circuit boards (PCBs). Electronic devices so made are called surface-mount devices or SMDs.
(definitions were from http://en.wikipedia.org/)

This device would gather GPS data and store it on the SD card so it could later be uploaded to a computer to determine where it (and also who/what its attached to) has been. There are many different uses for such a device, parents (or employers or the FBI) often use them to track where (and how fast) there child (or employee or suspect) has taken their car. Some people also just like to know where they have explored or how fast they biked or how far they ran.

[dchall8]

That's not what I thought at all. Now I want one.