Electronics

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Paradox21
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Electronics

Post by Paradox21 » September 27th, 2009, 6:31 pm

What is the best way to connect all of the wires, switches, resistors, and other electonic goodness? I thought I remembered hearing people say soldering was the way to go, but some of DS's MPC pictures use those twist on wire cap things, and I kind of like breadboards but I don't know if they would work well.
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Re: Electronics

Post by fleet130 » September 27th, 2009, 9:31 pm

What is the best way to connect all of the wires, switches, resistors, and other electronic goodness?
There's not just one answer to this question. When you're experimenting/prototyping, where frequent changes can be expected, just twisting the wires together, bread boards or wire nuts are the way to go.

Once you have a finalized design that won't need ANY more changes, solder connections are most reliable (if you know how to solder), but are not absolutely necessary (or even desirable) in some applications. If soldered connections need to be taken apart, a real possibility of destroying the parts in the process exists.

Until you learn how to solder properly, making even first-time connections can turn into a butcher job. Here are the basic steps, but you would be wise to research for more info.

Code: Select all

Note: Do not use acid based soldering paste/flux on electrical components.

1.  Surfaces to be joined (about 3/8in of the ends of wires and the terminals on switches and other components (especially on new parts) must be properly cleaned to allow for rapid heat transfer and so the solder can bond to BOTH surfaces. Use alcohol and a stiff, non-metallic brush (toothbrush works well-I like to use an acid brush with the bristles cut to about 1/4 inch long)

2.  Make sure your soldering iron is at the proper temperature, the tip of the iron is clean, and is freshly tinned (covered with a thin coat of solder).

3. Tin the portion of each piece to be joined.

	 a. Coat the cleaned portion of one of the pieced to be joined with liquid flux.
	 b. Melt a small amount of solder so it forms a small ball/drop of solder on the iron's tip.
	 c. Apply the melted solder on the tip of the iron to the cleaned portion of the part to be joined, 
	 applying a thin coat of solder to it.  Excess solder can be removed by quickly rubbing the 
	 part/iron on a damp paper towel before the solder solidifies.
	 d. Repeat for the other piece.

4. Next make a good tight mechanical connection that does not allow movement between the parts to be joined.

5. Make sure the soldering iron tip is clean and well tinned. You cannot recheck/redo this too often!

6. Apply a drop of liquid flux to the joint so both parts are wetted.

7. Before the flux evaporates, place the tip of the soldering iron so that it contacts BOTH pieces to be joined. Slowly count one, two, three.

8. Apply the solder so it touches BOTH pieces to be joined. The solder should begin to melt almost immediately. Melt just enough solder onto the joint to make a nice fillet between the pieces. Remove the un-melted piece of solder and watch for the solder to flow and fill the joint. The iron should not be in contact with the parts being soldered for more than 5-6 seconds. Longer contact can damage the parts.

9. Immediately after the solder flows to fill the joint, remove the soldering iron and let the solder solidify.

10. After it cools, the joint should have a bright, shiny appearance. If it looks dull, crystallized, has black spots or cracks, it stands a good chance of causing trouble later, even if it works fine now(you know when that will most likely be!

Don’t fall prey to the urge to take shortcuts in the process. Bad solder joints are often intermittent and can be VERY difficult to find.
  
Of course, practice makes perfect! Before you destroy parts you really need, practice on junk parts you don't need before attempting to solder the real thing.
Information expressed here is solely the opinion of the author. Any similarity to that of the management or any official instrument is purely coincidental! Doing Science Olympiad since 1987!

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Re: Electronics

Post by DeltaHat » October 5th, 2009, 9:28 am

My policy has always been to solder connections within an individual module, and use banana plug wires and terminal blocks to link modules together.

This arrangement gives you the flexability to bypas a module quickly without tearing your device appart.

http://en.wikipedia.org/wiki/Banana_connector
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Re: Electronics

Post by cypressfalls Robert » January 5th, 2010, 1:21 pm

Does radioshack sell temprature change sensors?

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Re: Electronics

Post by Dark Sabre » January 5th, 2010, 1:39 pm

I would imagine that they have thermistors...or they should. I searched the website for them and the Pots/Trimmers/Thermistors category appears to contain none of the latter.

Thermistors are a subcategory of resistors, so they should be allowed by most judges. Some temperature sensors are IC-based and thermocouples require some other external digital circuitry to be useful, so you may be limited to thermistors.

It depends on what exactly you are trying to achieve, but you can also use a coil of bimetallic strip (from an outdoor dial thermometer) to act as a temp sensor. As it heats up, the coil unwinds. I've used bimetallic strips to press buttons. The level of heat you need to get quick action pretty much mandates nichrome, since matches/candles are out this year.

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Re: Electronics

Post by Uncle Fester » January 5th, 2010, 9:12 pm

On a Mission Long Long Ago, I saw a team use one of those classic round home heating thermostats. I'd seen LOTS before, all run by a flame underneath, but this one worked by dumping hot water on it-- coil unwound and tripped the mercury tilt switch. Although these things are designed to run on 24VAC, wires were run directly to the switch, bypassing an internal relay (normally used in switching from heat to AC) as well as the hysteresis resistor.
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Re: Electronics

Post by cypressfalls Robert » January 5th, 2010, 9:23 pm

Uncle Fester wrote:On a Mission Long Long Ago, I saw a team use one of those classic round home heating thermostats. I'd seen LOTS before, all run by a flame underneath, but this one worked by dumping hot water on it-- coil unwound and tripped the mercury tilt switch. Although these things are designed to run on 24VAC, wires were run directly to the switch, bypassing an internal relay (normally used in switching from heat to AC) as well as the hysteresis resistor.
yea i was planning to do something similar with heating water.

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Re: Electronics

Post by Dark Sabre » January 6th, 2010, 6:35 am

cypressfalls_Robert wrote:
Uncle Fester wrote:On a Mission Long Long Ago, I saw a team use one of those classic round home heating thermostats. I'd seen LOTS before, all run by a flame underneath, but this one worked by dumping hot water on it-- coil unwound and tripped the mercury tilt switch. Although these things are designed to run on 24VAC, wires were run directly to the switch, bypassing an internal relay (normally used in switching from heat to AC) as well as the hysteresis resistor.
yea i was planning to do something similar with heating water.
Not sure what part of that you were planning to replicated, but remember that mercury tilt/expansion switches are out because of the no non-water liquids rule.

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Re: Electronics

Post by teamcosmos » January 10th, 2010, 10:46 am

can teams use a potentiometer ( a 3 terminal resister or variable resistor ) in this years mission possible. The rules say resistors are allowed but this is a more complicated resistor but would be helpful in varying the resistance.

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Re: Electronics

Post by Dark Sabre » January 10th, 2010, 11:10 am

If I were judging the machine, I would definitely allow pots, yes. They are just resistors with knobs.

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