Water Rocket Forum

We receive a number of questions regarding the ServoChron(tm) sent to our email and we're getting duplicate questions as time goes on, so we decided to start up a forum topic where we hope people will go with their questions. By posting the questions in public, it should be helpful to other people who have the same issues. If you have a ServoChron question, search this topic and you may find the answer you seek without having to go through the trouble of asking! If it's not here, feel free to ask, we are here to help!

I'll start off with a question:

There's a new kind of MSP430 board around, the "MSP430F5529 USB LaunchPad". (http://www.ti.com/ww/en/launchpad/msp430_head_usb.html)
I was wondering:

a) Does it have any advantages over the 'old' one? It's only $12.99 compared to the $10.00 MSP430 I'm currently using
b) Would it actually work if I'd like to put this one in my current setup? (So: uploading your firmware to it, connecting wires and such)

Thanks in advance.

Willem wrote:I'll start off with a question:

There's a new kind of MSP430 board around, the "MSP430F5529 USB LaunchPad". (http://www.ti.com/ww/en/launchpad/msp430_head_usb.html)
I was wondering:

a) Does it have any advantages over the 'old' one? It's only $12.99 compared to the $10.00 MSP430 I'm currently using
b) Would it actually work if I'd like to put this one in my current setup? (So: uploading your firmware to it, connecting wires and such)

Thanks in advance.

If you had been following our Twitter Feed, you would have known that we've been investigating the new Launchpad board for quite some time:

To begin with, this board is not compatible with the original LaunchPad which the ServoChron is based on, so the code has no chance of working, and the wiring connections are totally different. You cannot use this with the ServoChron project. If some popular movement springs up to support the new board we would happily consider it. The board does have some drawbacks for our application we will explain below.

Remember that TI makes a vast number of LaunchPad boards now... Read about them here: http://www.ti.com/ww/en/launchpad/overview_head.html

MSP430G2 Value Line Launchpad <---- ServoChron Version
MSP430F5529 USB Launchpad
C2000 Piccolo LaunchPad
Tiva™ C Series LaunchPad
Hercules TMS570LS04x/03x LaunchPad
Hercules RM42X LaunchPad

If you're looking for the best LaunchPad to use as a rocket project, the original MSP430 LaunchPad is a the best because it is the smallest and lightest and the easiest to program.

The negatives for the newest one, which you were asking about (MSP430F5529 USB LaunchPad ) is about 20% larger, and 30% heavier than the original. It also has connectors protruding about 1" from the top and bottom of the board, which makes it awkward to mount in a rocket. The CPU has a lot more options and peripherals, making it more powerful than the original LaunchPad, but also making it harder to learn and program.

If you are more interested in trying your hand at programming and have non rocket projects in mind, the Tiva™ C Series LaunchPad would be your best bet, because it uses an ARM core CPU which is an industry standard, so anything you learn by tinkering with this board will be useful for processors that many other companies produce. The Hercules versions are about 2x the cost and are targeted at a more niche market, but are also quite powerful themselves.

The important thing is to experiment and have fun!

I ordered two more MSP-EXP430G2 boards last week, and they came in the mail. I also bought a StratoLogger altimeter from PerfectFlite and I have still got the uMAD apogee detector from the folks over at Whooshtronics.
My idea was to combine these two apogee detectors (The StratoLogger has the ability to detect apogee) in case one of them fails. Why would one fail? Well, the StratoLogger has a 'Launch Detect Altitude' of 160 feet. If my rocket doesn't reach the 160ft and the only way to trigger the parachute was the StratoLogger I'd be in problems. So I'd like to have a backup.

But my question is: how should I wire all this up? When I had only one apogee detector, the uMAD, I just hooked up it's ejection charge GND to P1.7 and that worked fine. I can do the same for the StratoLogger but that still leaves me with 2 wires going to the same port and I'm concerned the two detectors will somehow interfere with each other.

Willem wrote:I ordered two more MSP-EXP430G2 boards last week, and they came in the mail. I also bought a StratoLogger altimeter from PerfectFlite and I have still got the uMAD apogee detector from the folks over at Whooshtronics.
My idea was to combine these two apogee detectors (The StratoLogger has the ability to detect apogee) in case one of them fails. Why would one fail? Well, the StratoLogger has a 'Launch Detect Altitude' of 160 feet. If my rocket doesn't reach the 160ft and the only way to trigger the parachute was the StratoLogger I'd be in problems. So I'd like to have a backup.

But my question is: how should I wire all this up? When I had only one apogee detector, the uMAD, I just hooked up it's ejection charge GND to P1.7 and that worked fine. I can do the same for the StratoLogger but that still leaves me with 2 wires going to the same port and I'm concerned the two detectors will somehow interfere with each other.

That depends. Since the Stratologger has a output designed to fire 9V electric matches, it would drive the input to the ServoChron too hard and would damage it. You would need to add a transistor to the apogee input (or an opto isolator) and translate the voltage level.

You also have the option of connecting the apogee trigger on the ServoChron to one of the circuit elements on the Stratologger itself. We use a compatible signal on the board we solder the connection to. But this is something people don't like to do, so maybe you wouldn't do it.

Hey all,
First of all thanks to those who put together this low cost/high performance deploy system. It really helps tinkerers like me to get a proper parachute deploy system in my rockets. I will be getting the parts soon.

Just 2 questions though.

1. Is there a kit of all parts available. I know the shopping around is not a drama but just thought I would ask.

2. I don't have a charger to charge the lipo cell and found this on Hobbyking.
http://www.hobbyking.com/hobbyking/stor ... arger.html
Is this suitable for the lipo cell listed in the bom?

MajorTom.

It will do the trick, but if your not going for a record than the extra weight of a 9 volt battery won't hurt and it works well even though they say it burns out the servo. I haven't had any experiences like this.

P.S. I just put mine together a month ago.

MajorTom wrote:Hey all,
First of all thanks to those who put together this low cost/high performance deploy system. It really helps tinkerers like me to get a proper parachute deploy system in my rockets. I will be getting the parts soon.

Just 2 questions though.

1. Is there a kit of all parts available. I know the shopping around is not a drama but just thought I would ask.

2. I don't have a charger to charge the lipo cell and found this on Hobbyking.
http://www.hobbyking.com/hobbyking/stor ... arger.html
Is this suitable for the lipo cell listed in the bom?

MajorTom.

This is what I have and why:
Not a fan of 9v. Also, If you decide to add LED lights to your rockets, the lipos are a nice match.

Everything has been fine if you wire the LED's correctly. My dad owns a charger similar. A traxxas charger that costs about $90

Thanks for the replys and advice guys,

I will probably go with the LiPo and small charger just because I am sure it will find a use in a future project down the road.

I am definately not going for a record just yet. Hard to tell without an altimeter but I don't think my single bottles have reached 100 meters yet.
I have spliced some 2 liter bottles and waiting for them to dry and will build a split ring cable tie launcer soon so should be able to ramp up my height accordingly.

Anyway, a break in the rain here so out to the back yard to test my air flap parachute deployment system.



Back soon with good news or another lawn dart experience.

MajorTom

About an altimeter, talk to bugwubber. He has one that cost only $30 and is a logging altimeter.

MajorTom wrote:Hey all,
First of all thanks to those who put together this low cost/high performance deploy system. It really helps tinkerers like me to get a proper parachute deploy system in my rockets. I will be getting the parts soon.

Just 2 questions though.

1. Is there a kit of all parts available. I know the shopping around is not a drama but just thought I would ask.

2. I don't have a charger to charge the lipo cell and found this on Hobbyking.
http://www.hobbyking.com/hobbyking/stor ... arger.html
Is this suitable for the lipo cell listed in the bom?

MajorTom.

Thanks for the kind words on the project. We're pleased that you have found it helpful.

Regarding a kit version, we don't sell such a thing. We're not really into selling stuff. We'd rather just share what we design and let others build it on their own.

Something to think about regarding chargers is that just about every LiPo powered trinket on the market will have a charger. We have a number of broken old 808 keychain type #3 cameras (you can get them NEW now for about $7.00). You can remove the battery and put a connector on it and use the camera battery for the ServoChron and use the camera to charge the battery. You put another connector on the camera and swap the battery back to the camera and charge it with a USB cable. This will work for anything. An olf MP3 player, a CellPhone, anything.

You can also buy a plastic holder that accepts 4 or 3 AAA batteries and use that for the servochron power. Those are pretty inexpensive too.

Water Rocket Expert wrote:It will do the trick, but if your not going for a record than the extra weight of a 9 volt battery won't hurt and it works well even though they say it burns out the servo. I haven't had any experiences like this.

P.S. I just put mine together a month ago.

Running a 5V servo on a 9V battery is probably not going to make it live a long life. However, if you use "depleted" batteries, it will be happy. Just measure the battery and see if it has 6V or so left in it.

From the readings I get on my meter, I see that the board limits the out put current to 5v no matter how much you put in as long as it is less than 10v and more than 4v. Even when using a 9v battery, the board puts out 5v to the motor. I have done some testing before using that battery so I am confident I know what I am talking about.

From the readings I get on my meter, I see that the board limits the out put current to 5v no matter how much you put in as long as it is less than 10v and more than 4v. Even when using a 9v battery, the board puts out 5v to the motor. I have done some testing before using that battery so I am confident I know what I am talking about.