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TI Launchpad Altimeter with display screen??

Discussion about deployment systems including altimeters, timers, air speed flaps, servo systems, and chemical reactions.
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captike
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TI Launchpad Altimeter with display screen??

Post by captike » Thu Jun 28, 2018 7:33 pm

I'm moving on to planning my altitude/parachute deployment system and have a question (in truth, probably a couple). I've thoroughly read the tutorial on building the TI Launchpad altimeter and I like it, however, I would really like one with a display screen for reading the altitude and instead of counting beeps. I saw this on the TI website and was wondering if anyone has or knows how to use it in place of the other one. Also, will the firmware on the same tutorial work on that board? I'm guessing that it won't, but wanted some kind of confirmation. I have no programming experience, but have experience with circuit boards and the like.



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anachronist
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Re: TI Launchpad Altimeter with display screen??

Post by anachronist » Thu Jun 28, 2018 7:43 pm

If you don't already have an investment in the TI, you might consider the Eggtimer Quantum. It has a built-in WiFi that transmits the data to your phone so you can view it immediately. It's like having a display, only remote. You don't need to know anything about programming, but you do need to know how to solder, because it's sold as a kit and you must solder it together.



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captike
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Re: TI Launchpad Altimeter with display screen??

Post by captike » Thu Jun 28, 2018 7:57 pm

Oh ok, I'll check them out. Two questions, can it trigger a parachute and is it affordable like the TI? I don't have anything right now, so I'm open to any options. :)



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Re: TI Launchpad Altimeter with display screen??

Post by captike » Thu Jun 28, 2018 8:24 pm

I took a cursory glance at it, and am definitely intrigued. I like the assembly aspect of it as well as the price. Have/do you use the Eggtimer with a servo similar to the one in tutorial for parachute deployment? If not, what is your setup for doing so?



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anachronist
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Re: TI Launchpad Altimeter with display screen??

Post by anachronist » Fri Jun 29, 2018 1:10 pm

Two questions, can it trigger a parachute and is it affordable like the TI?
It has two deployment modes. One will drive a servo and one will burn through a wire. You need to decide which mode you want when you build it. I recall the cost of the kit is $45.
Have/do you use the Eggtimer with a servo similar to the one in tutorial for parachute deployment? If not, what is your setup for doing so?
I posted a picture of my Eggtimer + servo + battery here: viewtopic.php?f=5&t=2994&p=19370&hilit=eggtimer#p19350 - click the picture to expand it. The white wire in the photo wasn't connected at the time, it would go to one of the negative terminal holes on the PC board.

I modified it a bit, like a using a battery connector in place of the fullwave bridge, and omitting all the binding posts. I saved a couple of grams that way.

To drive a servo, you need to build a small extra circuit (not included in the kit) consisting of two capacitors and a resistor. That's the tiny circuit in the picture on the servo wire. My servo is about 4g, which I found on eBay. The battery is 120mAh, which is probably the minimum size you should use, and way less than what Eggtimer recommends. However I find it's sufficient for a couple of flights before needing a recharge. I bought two batteries, which I swap out.



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anachronist
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Re: TI Launchpad Altimeter with display screen??

Post by anachronist » Fri Jun 29, 2018 1:13 pm

anachronist wrote:
Fri Jun 29, 2018 1:10 pm
Two questions, can it trigger a parachute and is it affordable like the TI?
It has two deployment modes. One will drive a servo and one will burn through a wire for pyro deployments. I posted a question about burning a wire in a water rocket and WRA2 answered that this would be OK. You could probably come up with a pretty lightweight mechanical deployment system in the pyro mode. You need to decide which mode you want when you build it. I recall the cost of the kit is $45.
Have/do you use the Eggtimer with a servo similar to the one in tutorial for parachute deployment? If not, what is your setup for doing so?
I posted a picture of my Eggtimer + servo + battery here: viewtopic.php?f=5&t=2994&p=19370&hilit=eggtimer#p19350 - click the picture to expand it. The white wire in the photo wasn't connected at the time, it would go to one of the negative terminal holes on the PC board.

I modified it a bit, like a using a battery connector in place of the fullwave bridge, and omitting all the binding posts. I saved a couple of grams that way.

To drive a servo, you need to build a small extra circuit (not included in the kit) consisting of two capacitors and a resistor. That's the tiny circuit in the picture on the servo wire. My servo is about 4g, which I found on eBay. The battery is 120mAh, which is probably the minimum size you should use, and way less than what Eggtimer recommends. However I find it's sufficient for a couple of flights before needing a recharge. I bought two batteries, which I swap out.



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Re: TI Launchpad Altimeter with display screen??

Post by captike » Fri Jun 29, 2018 6:05 pm

Thanks for that...some follow up questions. What is the fullwave bridge thing you speak of? I can't find any mention of that part on their website. Also, is it still necessary to build that extra circuit for the servo? I see on the Quantum product page it says "Built-in support for standard PVM hobby servos." Is it possible that the design has been changed since you built yours or am I confusing that with something else?



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Re: TI Launchpad Altimeter with display screen??

Post by anachronist » Fri Jun 29, 2018 6:52 pm

The fullwave bridge is mentioned in the assembly documentation on the website. It's component that allows the battery to be connected in either polarity without damaging anything. By substituting a battery socket and a jumper wire between two holes, I eliminated the fullwave bridge and the battery is always connected correctly because the socket allows only one way to plug in the battery. Notice that in my picture, I have spliced a connector plug onto the battery wire. I did this because those batteries came with a connector that wouldn't fit into a standard LiPo charger (the larger size batteries, like 150mAh and up, have the correct plugs). I bought a small package of connectors and socket pairs on Amazon.

The "built in support" for servos means that the Quantum sends the proper servo signals down the deployment line, rather than a burst of current to burn a wire or squib. The extra circuit is for providing power stability and noise filtering to the servo, to prevent jittering. This extra circuitry is not needed for pyro deployments, and pyro rockets (not water rockets) are the intended use for this altimeter.



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captike
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Re: TI Launchpad Altimeter with display screen??

Post by captike » Mon Jul 02, 2018 2:04 pm

I got you now. I read up on the Quantum the other day and have decided to go that route. I saw in the manual where it talks about the extra circuit needed for the servo. Is there any chance you have a wiring schematic for that? The instructions discuss it, but I'm not entirely clear where everything goes. I can read a wiring diagram a whole lot easier than a paragraph. BTW, thanks for all of your help.



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Re: TI Launchpad Altimeter with display screen??

Post by anachronist » Mon Jul 02, 2018 2:50 pm

Here's a schematic. The resistor and small capacitor cross over the red wire without contacting it. The '+' symbols are connections.
                      
white (signal) ------------------+----+-----> to servo
                                 |    |
                                 \    |  small
                        resistor /   === capacitor
                                 \    |
                                 |    |
red (power) ------+--------------|----|-----> to servo
                  |  large       |    |
                 === capacitor   |    |
                  |              |    |
black (ground) ---+--------------+----+-----> to servo

The large capacitor connected between power and ground provides some power stability to the servo. The resistor+capacitor on the signal line act as a low-pass filter to remove noise from the signal.



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captike
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Re: TI Launchpad Altimeter with display screen??

Post by captike » Thu Jul 05, 2018 6:00 pm

That's perfect!! Thank you! I've got my Quantum on order.



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Re: TI Launchpad Altimeter with display screen??

Post by anachronist » Thu Jul 05, 2018 11:37 pm

Be sure you have a 6-watt soldering iron and small wire clippers too, and double-check each step in the directions before you solder anything! Once I got in a hurry and ended up soldering the power transistor backwards, and it was a real pain to de-solder and pull out of the holes. Total time I spent on assembling it was several hours over the course of a week. My jeweler's loupe never arrived in time, so I wore 3 pairs of 2.5X reading glasses stacked on my nose to examine my work. You'll also need to order a servo, LiPo batteries, a charger, and a servo socket connector.



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captike
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Re: TI Launchpad Altimeter with display screen??

Post by captike » Sat Jul 14, 2018 3:55 pm

So, I just finished assembly of my Quantum and I have to say, it was a lot of fun. I really enjoy projects like this. It took me a couple hours over two days at work to complete assembly. For anyone else, Anachronist was correct, this little thing is pretty cool (and I haven't even flown with it yet). Cris over at Eggtimer has really made something special here and he's very helpful to boot! I still am waiting on my battery and pieces for the servo circuit, but want to make sure I have the wiring down for when they get here. In the attached picture can you verify my thoughts of where everything goes is correct? I'll be using the Main parachute on the Quantum and think the white wire from the servo circuit connects to the + pin on that header. Also, I'm not sure what to do with the white wire coming from the battery. Is it supposed to connect to nothing?? Please, let me know if everything else in the picture is correct. Thanks!!
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anachronist
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Re: TI Launchpad Altimeter with display screen??

Post by anachronist » Sat Jul 14, 2018 5:44 pm

The white wire of the battery is not used in the Eggtimer. You do need it for charging the battery though. A good LiPo charger is a balanced charger that charges each cell individually and your battery has two cells. The white wire is the tap between the two cells.



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Re: TI Launchpad Altimeter with display screen??

Post by captike » Sat Jul 14, 2018 8:03 pm

I gotcha. Is everything else correct on the diagram?



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