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LaunchPad AlTImeter without MSP430 Launchpad

Discussion about deployment systems including altimeters, timers, air speed flaps, servo systems, and chemical reactions.
uberpixel
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LaunchPad AlTImeter without MSP430 Launchpad

Post by uberpixel » Tue Sep 22, 2015 12:49 am

I've had a couple of inquiries regarding the standalone Launchpad AlTImeter that I built a while back so I thought I'd post a how-to thread.
140715_233721.jpg
140715_233627.jpg
140715_233616.jpg
140715_233602.jpg
My goal was a relatively barebones version of the AlTImeter which could operate without the MSP430 Launchpad board.

At the time I didn't want to get into etching my own PCB or using surface mount components - this had to be something I could easily put together in my garage without losing my mind...

The key to this layout is the Radio Shack 276-150 Multipurpose PCB. You can still find these in a Radio Shack near you (if you can still find a Radio Shack near you). Basically, you just cut the board down to use the portion necessary to fit the components. I cut mine so that I could make 2 assemblies out of one board, but I wish I had left a bit more on the board as a strain relief for the power and servo cables. This would have meant only getting one assembly per board, but the board is only a couple dollars and the extra strain relief would have kept me from breaking a power lead...

All connections are either made using the traces on the board or short jumper wires.

Here is the general layout (traces are shown but are in fact on the opposite side of the board):
mini_layout_final.jpg
And the parts list (all parts are from either Digikey, Sparkfun, or Radio Shack):
partslist.PNG
I'll add some step by step pictures soon showing the build steps to help clarify the hookup wire placement and a couple of tricks...

Also - for the detail oriented, you may notice that the LED's and LED resistors on my diagram look different from my build. As it turns out, the TI schematic for the MSP430 Launchpad board is incorrect and that is what I based my build on. I've updated the diagram to show the correct color LED's and the proper resistors for each. So - the diagram is correct, my build is wrong. You can check this on your actual MSP430 board if you want o double check.

-uberpixel
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uberpixel
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Re: LaunchPad AlTImeter without MSP430 Launchpad

Post by uberpixel » Tue Sep 22, 2015 9:49 am

uberpixel wrote:My goal was a relatively barebones version of the AlTImeter which could operate without the MSP430 Launchpad board.
I should add that you will still need the MSP430 Launchpad board for initial programming of the ICU chip... I've included an extra chip in the parts list if you want an extra.
uberpixel wrote:And the parts list (all parts are from either Digikey, Sparkfun, or Radio Shack):
And Hobby King for the servo, battery and cables...

-uberpixel



motorcyclepilot
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Re: LaunchPad AlTImeter without MSP430 Launchpad

Post by motorcyclepilot » Tue Sep 22, 2015 12:13 pm

That's great! Thanks for sharing. Now...where did I put my FTC's?



uberpixel
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Re: LaunchPad AlTImeter without MSP430 Launchpad

Post by uberpixel » Fri Sep 25, 2015 10:45 am

I would strongly recommend some sort of sun shade to protect the pressure sensor. I was really hoping to flip the Sparkfun board over so it wouldn't expose the sensor to the sun, but the layout really didn't lend itself to that orientation.

I had many false deployments on the launching pad due to the sun until I place a shield over the sensor. Obviously need to be careful not to block the pressure port...

-uberpixel



uberpixel
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Re: LaunchPad AlTImeter without MSP430 Launchpad

Post by uberpixel » Sun Oct 04, 2015 2:27 pm

First image shows comparative size of the cut down Radio Shack PCB vs the MSP430. I don't have any pictures of the "cutting down" process but I basically scored the board with utility knife, supported the board between two wood blocks in a vise and snapped off what I didn't need. I misspoke earlier and said you can get two complete assemblies out of one Radio Shack PCB. I was thinking of an earlier layout that I rejected in order to optimize the overall width. Again I recommend extending the length and including a better strain relief or connectors for the battery and servo leads.
140715_210316.jpg
Next, begin laying out components on the board. The primary reason for using the Radio Shack board is to leverage the common grounding and power rails that are provided. With these common rails, there are only a few jumpers necessary. It's important to start with the green jumper (connect SW2 to Ground) as shown below since the IC socket will actually cover the upper hole for the jumper. My layout avoids sharing holes for more than one component or jumper lead. If you're okay with sharing leads in single holes, you can adjust accordingly and just stick the jumper into another hole on the ground rail. This jumper is the only connection that is covered by the socket and all components and jumpers are placed on the top of the board (side without traces). The picture shows the jumper wire unstripped - but it was obviously stripped before soldering. I think I used 20ga solid for the jumpers.
140715_210943.jpg
Place the IC socket, SW1, and the next brown/purple jumper (connect P2.4 to DCV+). This jumper has to sneak between the IC socket and switch (SW1) but should squeak by. You can solder these components at this point (remove the IC first so you don't cook it).
140715_211442.jpg
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uberpixel
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Re: LaunchPad AlTImeter without MSP430 Launchpad

Post by uberpixel » Sun Oct 04, 2015 2:44 pm

Since some of the components will be in close proximity and would short out if not insulated, I pulled the insulation off of some Cat6 cable I had lying around and slid it over the leads on resistor (R32 270ohm). You could also use shrink tubing.
140715_210415.jpg
Picture shows incorrect 470ohm resistor - this should be R32 270ohm as shown on layout diagram above.
140715_215130.jpg
Showing placement of R32, blue jumper (from RESET to SW1[+] rail) and orange/yellow jumper (P1.7 to Servo [Signal] rail)
140715_215937.jpg
Showing placement of R27 (47kohm resistor) and green jumper (Piezo[-] to Grounding rail)
140715_221805.jpg
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uberpixel
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Re: LaunchPad AlTImeter without MSP430 Launchpad

Post by uberpixel » Sun Oct 04, 2015 3:00 pm

PICTURE SHOWS LED'S BACKWARDS - RED AND GREEN SHOULD BE REVERSED (above diagram is correct picture is wrong)

Again, I discovered after building that the Texas Instruments PDF schematic for the MSP430 is wrong. Both the LED color and the resistor values that they connect with are backwards. Not a huge deal - it still works, but if you want to match the MSP430 colors, just switch red for green and make sure you use the resistors as shown in the diagram and all will be fine.

Place brown/purple jumper (connect VCC to DCV[+] rail) and place LED's and R33 (470ohm) - picture shows incorrect 270ohm resistor - should be 470ohm.
140715_222934.jpg
Place green jumper (connect SW1 [-] to grounding rail)
140715_224427.jpg
Place blue jumper (connect P1.3 to SW2 [+] rail) and 6-pin male header strip.

Solder everything in place.
140715_225006.jpg
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uberpixel
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Re: LaunchPad AlTImeter without MSP430 Launchpad

Post by uberpixel » Sun Oct 04, 2015 3:05 pm

Place SW2 (and SW1 if not already placed)
140715_225728.jpg
Connect servo leads
140715_231128.jpg
Connect power leads
140715_232526.jpg
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uberpixel
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Re: LaunchPad AlTImeter without MSP430 Launchpad

Post by uberpixel » Sun Oct 04, 2015 3:14 pm

Protect piezo lead with same Cat6 insulation (or heatshrink) as shown previously and place as shown (Piezo[+] to P2.7 and Piezo[-] to GND)
140715_233401.jpg
See insulation on Piezo leads to protect from shorting
140715_233410.jpg
Solder 6-pin Female header to Sparkfun pressure breakout board and test fit. You can also bundle the leads and shrink tube them for reinforcement. If you leave a tail on the PCB, you could shrink tube the leads together over the PCB tail to help protect the connections. I pulled one of these leads out on my build and had to re-solder...
140715_233602.jpg
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uberpixel
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Re: LaunchPad AlTImeter without MSP430 Launchpad

Post by uberpixel » Sun Oct 04, 2015 3:16 pm

That's it. You're done.

Good luck. Let me know if you have any problems...

-uberpixel



motorcyclepilot
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Re: LaunchPad AlTImeter without MSP430 Launchpad

Post by motorcyclepilot » Sun Nov 22, 2015 4:03 pm

Thanks Uber for the detailed build instructions. Here's my build. I made a few modifications: I used DPST tactile switches, a larger footprint piezo, and a slightly different pcb blank. Due to space restrictions I used jumpers (solder bridges) on the bottom of the board for Vcc and Vss.

All goes well until the unit goes into launch detect mode at which point it immediately triggers the deployment servo.

I tried blocking all light to the altimeter board, but had same results. I suspect a solder joint or a floating input is the cause?

[youtube][/youtube]

First pic is my layout diagram.
Second pic is the completed project.
Third pic is the underside of board, note solder bridges for Vcc and Vss.
Last pic is the top of board with all components in place, except battery and servo leads.
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Problem solved?

Post by motorcyclepilot » Mon Nov 23, 2015 4:20 pm

I began troubleshooting by placing the MSP430 into a known working Launchpad board. It performed acceptably.

I then replaced the altimeter module with two others I had. Still not working properly with any module.

I tried covering the altimeter with a light proof enclosure (a clay bowl) but the problem persisted.

Out of desperation I covered the static port on the altimeter with my thumb while powering up and until launch detect mode. Upon removing my thumb it remained in launch detect mode and now works flawlessly on the bench. I am getting simulated altitude of 30-50 feet by blowing across the static port.

This seems odd that somehow the altimeter module would not work properly until covering it with my thumb one time. Magic touch?

I will post a video later of testing in a vacuum chamber.



uberpixel
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Re: LaunchPad AlTImeter without MSP430 Launchpad

Post by uberpixel » Mon Nov 23, 2015 5:09 pm

That behavior is odd and not what I experience during normal operation.

Do you have enough spare parts to build the circuit on a breadboard? That was how I started my build to make sure I hadn't goofed when modifying the layout. Once I confirmed operation I soldered it in place on the PCB.

Also, it looks like you caught it during your build, but your grid paper diagram shows the ground lead from S2 going to the (+) rail instead of the grounding (-) rail.

I'll take a closer look at your layout and see if anything else catches my eye.

-uberpixel



motorcyclepilot
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Re: LaunchPad AlTImeter without MSP430 Launchpad

Post by motorcyclepilot » Mon Nov 23, 2015 6:39 pm

uberpixel wrote:That behavior is odd and not what I experience during normal operation.

Do you have enough spare parts to build the circuit on a breadboard? That was how I started my build to make sure I hadn't goofed when modifying the layout. Once I confirmed operation I soldered it in place on the PCB.

Also, it looks like you caught it during your build, but your grid paper diagram shows the ground lead from S2 going to the (+) rail instead of the grounding (-) rail.

I'll take a closer look at your layout and see if anything else catches my eye.

-uberpixel
It's working great now. Just completed a series of simulated launches in my vacuum chamber. I'll post the results when I'm done massaging the data.

I have enough parts to build two more, but decided not to breadboard....I forget why. Hmmmm...no idea why.

Nice catch in the diagram. The switches are wired correctly and work perfectly. I initially soldered one in place 90 degrees off. Had to desolder :BD: and resolder in the correct orientation.

Here's the most recent test video: [youtube][/youtube]

Thanks again for your time and effort! TH:



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Test data

Post by motorcyclepilot » Mon Nov 23, 2015 9:06 pm

Haven't made a chart in years....

Here's my initial data:
501 ml vacuum chamber chart.png
I don't operate in those altitudes (yet) so I decided to try a larger chamber.
1940 ml vacuum chamber chart.png
I believe a more solid test apparatus would provide more consistent results. I think I'm flexing the lid without meaning to. This altimeter is very sensitive.
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