Okay super noob need helppppp - Page 1
Forum section: electronics / beginners

author: Shadetreeprops
author_rank: Regular Contributor
timestamp: February 29, 2016, 06:25:08 am
content: I have been desigining a circuit for 2 weeks now. this is where i amThe circuit is a set of LEDS, they are to light up in sequence, but not chase or flash or anthing, they light up one at a time till they are all lit up. well its 2 at a time, the last one is single. it to indicate full charge.I started with simple 9Vdc power supply, resistor, cap, leds, cap leds, cap leds, cap, leds. last led.... no go as the resistor was causing the cap to dischare to 0v infinatly and casuing a infinate voltage drop below the amount needed to run the caps. changing the resistor same issue just slower..since i have no scope i could not scope it out, i had to google it out. and run it in a simulator over and over and watch each issue.so then i think let me try transistors.. between each set of Leds, 1 resistor for just the leds after the first transistor, then to one resistor to the transistor B gate. so most electrons will flow to A and wait for gate B, to let I flow though C...using caps between the transistors, to slow the flow, and then open B gate to let I flow though A and C....and then i took the resistor out going to the transistors, becasue same thing voltage drop...fail fail fail.HERE ARE MY CRAPPY SCHEMATICS THEY ARE BAD i did not want to show these messy mucks off but here.ran the sims 100 times changing things.i had 1 resistor after the transitor right at gate C to limit current to LEDS so they dont POOF OUT... and the 100uF 16v caps were at Gate B of each transistor.. so they charge release the 5v needed to open gate and A go to C. but still FAILand sadly i cant show it to you.. becasue my local radioshack did not have bread board, and so all i got is several drawing, lots of math surrounding them. and the free sim i have to make over and over becasue it dose not want to save my circut..and all the stuff on google is not exactly like this..and i want to to act like the charge indicator on WAL-E one led set next and next and next till all 4 sets light up. then the last led lights up to say full...no matter what i google i get...chase lights, sequencer that flashes one at a time...its like a charger for a camera flash. it will indicate full charge show the charge indicated by lights...but once i get this part done the next part is to make it discharge all the caps to you guessed it make a flash flash...its for another prop gun project. and i have 3 going at once..but i have been beating my head on the wall with this one every day now..and i do not get much time between work and family to work on it.casue this should be simple..but i am missing something somewhere.

author: Psi
author_rank: Super Contributor
timestamp: February 29, 2016, 06:36:17 am
content: LM3914 is what you want.Basically lets you connect LEDs up and it will illuminate them based on the voltage level you feed it.It can be set in either dot or bar mode (so like a bar graph /or/ like a single moving led)Once you have configured the thresholds with the resistors it will display the voltage you feed it on the LEDs like a bargraph multimeter.

author: Psi
author_rank: Super Contributor
timestamp: February 29, 2016, 06:47:08 am
content: This uses LM3915 which is similar but logarithmic which is good for audio, (you want the LM3914 which is linear and good for voltage display)

author: Shadetreeprops
author_rank: Regular Contributor
timestamp: February 29, 2016, 07:01:39 am
content: this makes me want to cry...i have not really worked with IC chips so i was not even thinking that way...but this this was easy...soo easyim a moron.jeez thank you for making my life eazier..before you know it i would have designed this chip without even knowing it..lol OH and my eye twitch went away after seeing this.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: February 29, 2016, 07:32:54 pm
content: The LM3914 is a workable solution, but really, this project cries out for an Arduino. A simple sketch, a three-dollar Pro-Mini clone + USB programmer interface, add the LEDs and their resistors and you're done.Want to change the timing or order of LED flashing? Just change a few lines of code in the sketch. Need to add or subtract LEDs? Just change the code. Want to control multicolor LEDs, add sound, etc? Simple with the Arduino solution.As an electronic prop-builder, one might want the versatility that a microprocessor can add. It could be worth it to spend a few hours playing around with basic programming in the Arduino IDE if you want to make LEDs do whatever you want them to do.Of course, you'll learn a lot more about electronic theory if you make some circuit out of transistors or the LM3914 that does what you want. No argument there. (What happens if you want to run 12 LEDs instead of 10, or change the timing of the sequence, though? Out comes the soldering iron, more and different components, etc.)

author: Shadetreeprops
author_rank: Regular Contributor
timestamp: February 29, 2016, 09:36:09 pm
content: well im a noob, i really want to grasp the circuits first..then maybe try to take on arduino..i do not care much for programming though, as i studied C++ and Java and did not like doing either.but i guess code for some lights and timing would be much easier than say trying to write a game program, or build my own calculator to do all my work for me. by selecting the equation and the math type...<<<what i was doing with C++ 2 years and wasted time to lose everything casue i did not think to back everything up in casue of a system failure..casue im such a genius....but by looking at my crap schematics was i on the right path, but taking the wrong road to get there...or something like that?

author: Keridos
author_rank: Newbie
timestamp: March 01, 2016, 11:48:20 am
content: If you want to light up things in sequence you can also take 2 chips like a counter (CD4017) and a timer (NE555 f.ex.)The NE555 with a few parts just generates a clock signal and the counter counts up on each clock, and activating the next output port. Can be reset after x steps by just connecting the first unused step to the reset pin. The arduino is a simple way to understand the logic behind that, but in my opinion a microcontroller is pretty much overkill if you just want to light up a few leds. It gets interesting when you want animation and dimming (via PWM) but for simple on off of less than lets say 10 LEDs, a uC is too much.

author: rsjsouza
author_rank: Super Contributor
timestamp: March 01, 2016, 02:45:07 pm
content: I couldn't quite grasp exactly what you intend to do with the circuit, but you are on the right track with the transistor approach.If you want a voltmeter or ohmeter with LEDs, you can either usezenersortransistors.By the way, this last page sends you to a very interesting collection of electronic circuits by Colin Mitchell.http://www.talkingelectronics.com/Also, as others suggested, using a LM3914 will give you a more compact assemble:http://www.ti.com/lit/an/snva584/snva584.pdfAlso, to be honest, don't go the Arduino route just yet - microcontrollers cannot drive large loads without something in between - usually a transistor, a relay or both. If you understand and experiment with transistors (and electronics in general) you will be one step ahead of the pure embedded programmer.

author: Shadetreeprops
author_rank: Regular Contributor
timestamp: March 01, 2016, 04:15:28 pm
content: Quote from: rsjsouza on March 01, 2016, 02:45:07 pmwell thats just sad, but considering that is the 2nd time i have ever drawn a schematic, and i have only been at this maybe 2 months at best. Guess i cannot expect much.

author: Audioguru
author_rank: Super Contributor
timestamp: March 01, 2016, 04:34:52 pm
content: If you look at the datasheet of the LM3914 it shows you how to make the LEDs light as a moving dot or as a bar. It also explains that all outputs have adjustable current limiting so that current-limiting resistors are not needed for the LEDs.You talked about all LEDs to light up indicating a full charge. Are you charging a battery? What kind (chemistry) of battery? What limits the charging current? What prevents over-charging?

author: Shadetreeprops
author_rank: Regular Contributor
timestamp: March 01, 2016, 11:43:46 pm
content: Quote from: Audioguru on March 01, 2016, 04:34:52 pmNo its for a prop gun, for a fake phaser..basically the bar reads a full charge, but when i pull the trigger it cuts the circuit off, turning the lights off, and when released, the charge bar gose back up. so as if fake fires looks like its using up a fake power cell. the battery to power the circuit is going to be a 9v.my profile picture is actually one of my first non functional props.

author: Audioguru
author_rank: Super Contributor
timestamp: March 02, 2016, 12:53:02 am
content: Yes, you can use a charging capacitor and an LM3914 bar graph showing its rising voltage and a trigger switch can discharge the capacitor.

author: Psi
author_rank: Super Contributor
timestamp: March 05, 2016, 11:27:15 am
content: Quote from: Shadetreeprops on February 29, 2016, 09:36:09 pmCoding is like talking, weather or not it's enjoyable depends entirely on what your saying and why.Coding something youre passionate about is funCoding pointless uni projects is boringThat said..The key is learning to enjoy the symmetry and the beauty of perfect code.Then you can enjoy coding anything.

author: Brumby
author_rank: Unknown
timestamp: March 05, 2016, 11:41:40 am
content: Quote from: Psi on March 05, 2016, 11:27:15 amDare to dream.....

author: Shadetreeprops
author_rank: Regular Contributor
timestamp: March 05, 2016, 07:13:45 pm
content: I liked C++ it was easy compared to Java, but i lost my taste for it, when i lost a entire program i was writing. Then i got out of practice, and decided to not bother anymore.Then I started Java, but it is like talking like yoda, and having to over explain everything to get a simple end result.if arduino is as easy as C or C++ then i might start learing. But then comes the whole need of a IC programmer, ETC ETC. gear i do not have monies for.

author: Zero999
author_rank: Super Contributor
timestamp: March 05, 2016, 07:48:34 pm
content: The LM3914 is very expensive.What are you trying to do? Just make some LEDs turn on, one after the other?This can be done with some logic gates and RC circuits.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: March 05, 2016, 08:20:04 pm
content: For certain values of "very expensive".... check Ebay for some examples. Like 10 for 12.98, free shipping US seller. Or 5, plus 5 10-LED three-color bargraphs, for 10.99, US seller. If you want to order from China, you can get them for under 25 cents a piece, free shipping.The OP wants the LEDs to indicate state-of-charge of a capacitor, not just light up in a timed sequence. The LM3914 is perfect for the task.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: March 05, 2016, 08:26:54 pm
content: Quote from: Shadetreeprops on March 05, 2016, 07:13:45 pmThe Arduino IDE (the programming environment) uses a flavor of C/C++, you can download it from the Arduino website and look at the many example programs (called "sketches") and see how easy it is. The Arduino UNO and many other variants of the hardware do not need any separate programmer, just a plain old USB cable to connect to your computer. When it's plugged in via the USB cable, it is also powered through the cable so you don't even need a separate power supply. When it's not plugged in to the USB you can power it with any 7-12VDC source through the standard barrel jack. Some other Arduino variants like the Pro Mini (my favorite, around 3 dollars each from China) do need a separate interface for the USB connection, which costs another couple of dollars, and you only need one.

author: Psi
author_rank: Super Contributor
timestamp: March 05, 2016, 10:16:24 pm
content: Quote from: Hero999 on March 05, 2016, 07:48:34 pmYeah, it's so expensive. You have to pay a full $10 for 50 of them.http://www.aliexpress.com/item/50pcs-lots-Free-shipping-LM3914N-1-LM3914N-LM3914-The-Original/2047262862.html

author: LordHexahedron
author_rank: Contributor
timestamp: March 06, 2016, 11:22:18 pm
content: Quote from: Hero999 on March 05, 2016, 07:48:34 pm$2.35 for 10xLM3914N isn't that expensive

author: Shadetreeprops
author_rank: Regular Contributor
timestamp: March 06, 2016, 11:52:47 pm
content: Quote from: LordHexahedron on March 06, 2016, 11:22:18 pmI got 50 of them for 10 dollars, and 20 bar graphs for 10...so good now lol.but it wont stop me from copying this circuit down for furture projects.

author: LordHexahedron
author_rank: Contributor
timestamp: March 07, 2016, 07:07:45 am
content: Quote from: Shadetreeprops on March 06, 2016, 11:52:47 pmNice deal.As for the bar graph: why copy it down when you can just save the image and save the trouble? (unless you really want a paper copy I guess)

author: Shadetreeprops
author_rank: Regular Contributor
timestamp: March 07, 2016, 12:56:13 pm
content: Quote from: LordHexahedron on March 07, 2016, 07:07:45 amI did both, saved it to computer, and printed a copy out for myself. becasue i will not always be at my computer when working with electronics. but for anyone who want to know, i now undertstand the 555 timer. was having all kinds of problems not grasping the how it did what it did.