Show Posts
Pages: 1 2 3 [4] 5 6 ... 169
46  Using Arduino / General Electronics / Re: Soldering Hell on: January 12, 2013, 10:09:31 am
Quote
The bridges are on the board crossing the pads. 

Do your boards have soldermask?

This stuff isn't just for looks, it's actually more "solder-phobic" than bare substrate. When I made my own boards I found they'd bridge quite badly as compared to boards with soldermask.

-j
47  Using Arduino / Project Guidance / Re: How to make a timer for Rocket stage separation on: December 28, 2012, 03:20:58 pm
Quote
i could also use a gyro to mantain a stable fly and use small aleirons to correct the course (im also a RC plane builder) and i could achieve a less balistic flight ang get a higher apogee

You're crossing the line between a rocket and a missile.  Most governments are pretty aggressive about maintaining their monopoly on missiles. smiley-neutral

Use simulation and modeling (e.g. openrocket or rocksim) to simulate the rocket's flight.  If you feed measurements and test flight data back into it, the simulation will be quite accurate.

Among the simulation inputs are the launch rail angle, rail length, cross wind, etc. Getting all these right will accomplish a maximum altitude about as good as you could get, even with active control, and it'll be a lot easier and safer than trying to implement active control.

-j
48  Using Arduino / Project Guidance / Re: How to make a timer for Rocket stage separation on: December 23, 2012, 06:49:01 pm
Yes, an arduino can do that, although you'll need to add some transistors to switch the larger currents required for a typical e-match/igniter, and you'll need some sort of sensor (e.g. accelerometer) to detect events like launch, burnout of the previous stage, etc.

An accelerometer based system is nice because different motors have different burn times.  If you use a timer, the timer will have to be adjusted for each motor burn time.

-j
49  Using Arduino / General Electronics / Re: Opinions on soldering iron + hot air stations on: December 19, 2012, 10:16:27 am
Quote
If you're just starting out, just buy whatever "iron" or "system" you want/can afford.
Don't worry about it. They'll all do the job more or less.

But as your skills or needs increase, you'll begin to see the limits (or irritations) of the tools you have. -- then you'll exactly know what features you want from the high end models. Then you can spring for the higher, expensive model and you'll know/appreciate it's value more. Only you can tell when the time is right for *YOU* to "upgrade."

this pretty much sums up my advice.  I used a radio shack iron for many years.

If you get a chance to try a better unit (e.g. a friend, work, school, etc) you can see if you have outgrown the one you're using.

I used a Chinese knock-off of a Hakko iron at home for a few years, but used a real Hakko at work.  After a while I started watching ebay until I found a used Hakko unit I was willing/able to pay for.  I had the luxury of doing hot air at work, until I managed a good deal on a Hakko hot air station for the home shop.

-j
50  Community / Bar Sport / Re: iTead's "open source" option, I don't get it. on: December 14, 2012, 11:53:40 am
It's been a while since I noticed this, but I think they are encouraging you to open source the board, so if it's cool they can copy it and sell it themselves.

-j
51  Using Arduino / Microcontrollers / Re: ...a hand explaining this RAM shield please? on: December 13, 2012, 10:53:25 am
If you don't have a bajillion extra pins for the address and data lines, there are SPI interfaced RAM ICs.  I think there are libraries for some of the Microchip devices.

IIRC the microchip devices are 3.3V, so if you're running at 5V you may need a level converter.

-j
52  Using Arduino / Project Guidance / Re: Bullet sensor build help on: December 11, 2012, 11:45:50 am
Quote
very interesting that all your chrono needed was to watch for a drop in light.  I'm wondering how far above the sensors the bullet can be as still be detected.

The window is a triangle about a foot or 18" tall.

I just visited the manufacturer's web site (not much hard data there), looks like some of their newer models include IR illuminators, so it's watching for a reflection rather than a shadow.  The older passive models are still available.

-j
53  Using Arduino / Project Guidance / Re: Bullet sensor build help on: December 10, 2012, 11:05:26 am
IIRC, my crono doesn't have an emitter, just detectors.  I think it uses photoresistors, and watches for the drop in light caused by the shadow of the bullet passing over the sensor.

My crono is also about 20 years old; technology may have changed.  Still works, though.

-j
54  Community / Bar Sport / Re: I hate RF ! on: December 04, 2012, 10:07:47 am
depends on how much metal there is at the antenna mounting point.

If it's a metal box that is a significant portion on 1/4 wave, ground the coax on the box and use the box for your ground plane.  If you have much power, this could be unpleasant for the electronics inside. smiley-neutral

-j
55  Development / Other Hardware Development / Re: Arduino 1.0.1 causes Mac OS X to crash regularly. Ideas? on: December 03, 2012, 09:38:18 am
Quote
I don't consider "immediate reboots" and "kernel panics" to be the same thing.

Maybe not, but a kernel panic usually causes a reboot...

-j
56  Using Arduino / Project Guidance / Re: Solder paste vs. flux for reflow. on: December 03, 2012, 09:36:23 am
The guy I bought from on ebay doesn't list any for sale currently.  He was repachaging into syringes and I think I got mine for around US$10 a couple of years ago; I'm still using it.

Be careful, because there's some confusion among some sellers (seems to be a translation problem, maybe) about the difference between "paste flux" and "solder paste".  Paste flux is just that, flux in a paste form (as opposed to liquid) - there's no solder in it.  Solder paste is solder with the flux mixed in.

I got some paste flux from deal extreme.  It worked, but was a bit stiff, and not easy to dispense.

If it doesn't come in a syringe, get yourself some syringes and some dispensing tips.  I bought something like this so I had room to experiment.  You want dispensing tips, not needles - needles are sharpened, dispensing tips are not.

-j
57  Using Arduino / Project Guidance / Re: Quadcopter stabilization algorithm on: November 29, 2012, 10:46:00 pm
Quote
What 'other control algorithms' are you thinking of?

I think it was suggested sliding mode would be superior, but I've slept quite a few times since that discussion so I don't remember for sure.

-j
58  Using Arduino / Project Guidance / Re: Quadcopter stabilization algorithm on: November 29, 2012, 10:48:21 am
Quote
PID algorithms in the manufacturing process can be quite complex.  I believe this problem is simpler to solve.

Please elaborate.

Around here (university engineering department that teaches controls) the consensus seems to be that PID is less effective than other control algorithms, but it is used because it is simpler (to implement and understand).

-j
59  Using Arduino / Sensors / Re: Fast response temperature sensor recommendation? on: November 28, 2012, 09:25:44 am
Quote
The speed of Dallas depends on the resolution 9..12 bit  == 8 integral part and 1..4 bits decimal part

Er, I think the speed depends on the (insulating) plastic case the part is in...

If you need fast sensor response time, look for sensors that are not in plastic cases - e.g. a bare thermocouple junction.  I haven't dealt with RTDs or thermistors, maybe those can respond quickly as well.

You've got separate time issues here: the time it takes the actual (analog) sensor to reflect a change in environmental temperature, and the "conversion time", which is the time it takes to get that analog sensor value converted to digital.

You also need to look at the speed your sensor (or the air around it) is moving, and see if the speed you think you need makes sense.  For example:

You use a sensor/ADC combo that requires 10ms to sample and return a value.  Say you put this on a weather balloon with a 1000 ft/min ascent rate.  During the 10ms period, the balloon will rise 0.2 inches.  Do you really need 2 tenths of an inch resolution?

If you're not flying the sensor, maybe you should describe your setup and what you're trying to measure.

-j
60  Topics / Product Design / Re: Draw disconnected nets in Eagle? on: November 20, 2012, 11:14:02 am
codlink's method is what I use.

If you want to take it one step further and get the flag style labels, click info ("i" icon), then select the label in question.  check the "Xref" box, and the label transforms from floating text to text in a box.

-j
Pages: 1 2 3 [4] 5 6 ... 169