I have two blue flashing leds and I plan on lighting them with a portable power pack of 12v. (there are other leds involved, but they are on a seperate circuit board that I had purchased).
Now, is this the correct info that I have gathered?
I wire the leds in parellel and use just one resistor attached to the positive led. That one resisistor is based on the ohms rated for one flashing blue led. Because it is in parellel, that is the reason why only one is needed?
No thats not right, itme sin parallel should have all their own components, other wise you have a series parallel combo.
Trace the path of electricity:
Power comes out of the battery, it goes through the resistor, then some splits off and goes to either path of the blue LED.
What you need is one resistor for each LED so that when one LED is starting to flash off, the current doesn't spike into the other LED.
The resistor will be picked to operate at some current, if it is providing current for 2 LEDS and one LED goes out, the extra current now flows through the one LED. In a flashing circuit this will be happening often and the LEDs will probably die fairly quickly.
I have always read that the resistor is to be attached on the positive side.
But, my last statement was regarding what does this mean?
itme sin parallel
But from what Sparky is basically saying, is that I have to have one resistor for each flashing led. I cannot be joining the two leds together and have one resistor take care of both of them.
Well, that is certainly going to make it crowded in the kit with all those leds and resistors!
It doesn't matter which side of a led you attach the resistor to. It is good to pick one side and use that one consistently. If you wire up many leds/resistors at once, it is vital to be consistent.
I've heard of people using one resistor for more than one led (in parallel), but I don't do that. I always use 1 led = 1 resistor.
Normally you can use one Resistor for more than one LED, the draw back as mentioned is that the resistor is calculated for the total current draw of all the LEDs, if one fails or in this case is flashing the current delivered to the rest of the LEDs spikes (when flahsing and jumps to a higher level perminately for LEDs that go out).
This will take life off and or kill the other LEDs. Everytime an LED blinks the current it normally uses flows throw the other LEDs. This is why single resistors for multiple LEDs arent' a good idea, you should use a regulator to get the right current/voltage for a bunch of LED's wired in parallel.
A resistor is for steady state conditions, blinking is not steady state.
BTW the resistor can go on either side of the power supply, it is by convention that the ground or negative goes striaght to the battery.
However you place it you need to draw the circuit so you can see how current flows and where voltages are present.
It helps you seee that the current for all the LEDs pass through the resistor (Current is additive), and therefor if one LED goes out, there is more current left over than you had previously accounted for, it will now have to flow threw the other LEDs, they now conduct more current than they should.
Sparky has it right - draw out all your wiring so you know where everything is going to go.
But...
Build the circuit OUTSIDE of the model - on an experimenter's "bread board" - FIRST and let it RUN for a while so the problems (if any) are easily identified and corrected before you plunk anything into a model where it might be horrible to repair.
I do this "Build it where you can fiddle with it" a lot. Saves me from tearing out what hair I have left.
Question: Blue blinking LEDs? Do they blink by themselves (some LEDs have built in blinky chips) or are they being blunk by an outside source?
The first trick is in placing your major components, you place the parts so there is room to have parts nearby jumpered to the right place. Say a 3 terminal variable resistor, very comon in making flashing circuits, you wnat there to be a few slots free around the chip so that you can jumper the connection from the pin of the chip to one leg and the variable resistor, the other connection to the chip and anytoher connections needed.
A quick look at wiki realyl helps understand how breadboards are used, just in seeing how their internall connections are layed out helps you see why one is used.
It also helps you to make circuit boards, you lay it out on the bread baords, then build another one (don't take apart the breadboarded one) and follow/copy the physical layout on your soldered version.
Bread boards are the basis of hands on. You take a schematic and hand wire all the connections based on what the schematic shows, then give it a try.
The great advantage to soldering something up is you remove the variable of whether or not you over heated something, static shocked it with a bad iron, cold solder joint (ask me how I know about those), or shorted solder joint.
My board in that picture actually has several separate circuits on it, the one thing I found out early on much to my chagrin, was that although the strips down the sides (commonly used as power) look like the run continuously, they don't I had a circuit at the bottom of the board that wasn't working couldn't figure out why, then I realized that the strips have a break in them half way down, had to add jumpers to get power and ground from the top all the way down to the bottom.
If your breadboard comes with an overlay showing its busses, pin it up somewhere to help remind you of what squares are connected to where.
starmanmm wrote:
Ok now you are scaring me with that photo!!
Me too...so I've got good enough to skip all that. I just read the schematic and take it from Adobe Illustrator to clear film to etched copper clad board prototype within the day. Well....mayby the WWB circuits for TOS took a few more days. But it was the first circuit I buildt without the bread board phase.
I still can't figure out a voltage regulator circuit board with a LM317...I want to etch a few out to drop votages from 9 or 12 down to 5 or 6. That bread board set up still vexes me!
I've been working with electronics since I was in my early teens, and a breadboard is one of the best tools you can have, especially for analog circuits (with the exception of low noise/high gain/high bandwidth circuits).
The breadboard setup is really good when you are trying to tweek a circuit to get the look of some FX, flash rates, mixing of LED colors. If you have a circuit which won't need to be modified you can go right to the poto-board stage. But the layout and wiring techniques you learn on the breadboard or proto board will apply to both and to a lesser extent to when you start laying out etch patterns.
jwrjr wrote:The nice thing about working with single-chip computers is that the circuit tends to be very simple. Where it gets complicated is the software.
That's what scares me. I am okay with spending hours sitting at the 'bench, but sitting for hours working on a program I am not really able to do.
If a redhead works at a bakery, does that make him a gingerbread man?
With the PIC series controller, the software comes with a simulator, where you can get most of the bugs out. Even better, it comes with a 'C' compiler. If you use one of the 'flash' controllers, if you make a mistake you can pull the chip out, program over it, and put it back in.
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