| Electronics > Beginners |
| How to wire this setup? |
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| Brumby:
--- Quote from: MarkF on May 17, 2018, 04:09:09 am --- * The Arduino GND and the 12V GND should be connected together. Your 12V supply IS isolated? Correct? --- End quote --- This would be the FIRST thing I would attend to. |
| Youkai:
--- Quote from: MarkF on May 17, 2018, 04:09:09 am ---Looking at your breadboard picture, the emitters and collectors are swapped. --- End quote --- If you look at the circuit picture I posted in the top right is the transistor image. I'm pretty sure on my transistor the C/E are swapped from the picture you posted. Am I really just completely brain farting on how I'm interpreting the image? I swear I tried this before and it caused some sort of weird crossover. I turned the transistors around and it's working now at a much more reasonable brightness. So one problem solved. Yay! --- Quote from: MarkF on May 17, 2018, 04:09:09 am ---The Arduino GND and the 12V GND should be connected together. --- End quote --- Also looking at your diagram how do I connect the arduino and grounds from the LED together? Do I just run a wire from the ground rail on my breadboard to the ground pin on the arduino? Won't that cause all of the current to run through the arduino? I would think that might be bad for it. In the final product everything will be powered by the 12V supply so if I use that ground for everything then it is effectively tied together correct? --- Quote from: MarkF on May 17, 2018, 04:09:09 am ---Your 12V supply IS isolated? Correct? --- End quote --- What does this mean? I don't know how to answer. --- Quote from: MarkF on May 17, 2018, 04:09:09 am ---How many LEDs of each color are you trying to drive? Each LED will drop somewhere in the 1V to 2V range depending on the color. Driving them with 12V, you will only be able to drive about 6 LEDs of each color. I'm assuming the LEDs in the strip for each color are connected in series. I can't tell from the spec sheet. --- End quote --- One segment of the strip currently so 3 LED. Eventually I will be using 2 segments so 6 LED total. I'll also be running the arduino and 3 servo's off of the power supply. The arduino and servo's after it goes through a buck converter. So I need to make sure the power supply has enough amps/voltage to run all of that? --- Quote from: MarkF on May 17, 2018, 04:30:11 am ---Guessing from the picture of the strip, the current limit resistors (R4, R5, R6) are part of the strip for each group of 3 and you don't need them in your circuit. --- End quote --- Someone said in an earlier post that those were current limiting resistors. My current power supply only produces 500mA. Do I need to find a supply that produces more amps? Does the voltage of it matter; or will the current limiting resistors keep that to a value that will work for the strip? Where would I go to look for a wall outlet power supply? I tried the thrift shop to get this one but I'm guessing I should just find a site online that can sell me exactly what I need. MarkF, what tool did you use to draw your diagram? |
| MarkF:
--- Quote from: Youkai on May 17, 2018, 05:42:49 am --- --- Quote from: MarkF on May 17, 2018, 04:09:09 am ---Looking at your breadboard picture, the emitters and collectors are swapped. --- End quote --- If you look at the circuit picture I posted in the top right is the transistor image. I'm pretty sure on my transistor the C/E are swapped from the picture you posted. Am I really just completely brain farting on how I'm interpreting the image? I swear I tried this before and it caused some sort of weird crossover. I turned the transistors around and it's working now at a much more reasonable brightness. So one problem solved. Yay! --- End quote --- I downloaded the spec sheet for a 2N3904 transistor: http://www.onsemi.com/pub/Collateral/2N3903-D.PDF --- Quote --- --- Quote from: MarkF on May 17, 2018, 04:09:09 am ---The Arduino GND and the 12V GND should be connected together. --- End quote --- Also looking at your diagram how do I connect the arduino and grounds from the LED together? Do I just run a wire from the ground rail on my breadboard to the ground pin on the arduino? Won't that cause all of the current to run through the arduino? I would think that might be bad for it. In the final product everything will be powered by the 12V supply so if I use that ground for everything then it is effectively tied together correct? --- End quote --- Yes. Just run a ground wire from the Arduino ground pin to the ground on the breadboard. This provides a reference for the Arduino signals to turn on/off each transistor. Dave did a video on "How not to blowup your scope" that maybe helpful: --- Quote --- --- Quote from: MarkF on May 17, 2018, 04:09:09 am ---Your 12V supply IS isolated? Correct? --- End quote --- What does this mean? I don't know how to answer. --- End quote --- THIS IS IMPORTANT FOR THIS AND OTHER PROJECTS YOU CONNECT YOUR ARDUINO TO. IF YOUR PROJECT GROUND IS NOT FLOATING, YOU COULD SEND A VOLTAGE INTO THE GROUND PIN OF THE ARDUINO AND DESTROY IT. MOST LIKELY, THE USB PORT CONNECTED TO YOUR COMPUTER IS PROVIDING A GROUND THROUGH TO COMPUTER'S POWER SUPPLY. Isolated (or floating) means there is NO connection between the AC Power of the 12V supply and the DC output. I would disconnect your wall-wart and do a continuity check between each AC prong and each DC output pin. --- Quote --- --- Quote from: MarkF on May 17, 2018, 04:09:09 am ---How many LEDs of each color are you trying to drive? Each LED will drop somewhere in the 1V to 2V range depending on the color. Driving them with 12V, you will only be able to drive about 6 LEDs of each color. I'm assuming the LEDs in the strip for each color are connected in series. I can't tell from the spec sheet. --- End quote --- One segment of the strip currently so 3 LED. Eventually I will be using 2 segments so 6 LED total. I'll also be running the arduino and 3 servo's off of the power supply. The arduino and servo's after it goes through a buck converter. So I need to make sure the power supply has enough amps/voltage to run all of that? --- End quote --- I can only address the LED strip requirements. You will have to determine your total power requirements. I don't know what more you intend to do. --- Quote --- --- Quote from: MarkF on May 17, 2018, 04:30:11 am ---Guessing from the picture of the strip, the current limit resistors (R4, R5, R6) are part of the strip for each group of 3 and you don't need them in your circuit. --- End quote --- Someone said in an earlier post that those were current limiting resistors. My current power supply only produces 500mA. Do I need to find a supply that produces more amps? Does the voltage of it matter; or will the current limiting resistors keep that to a value that will work for the strip? Where would I go to look for a wall outlet power supply? I tried the thrift shop to get this one but I'm guessing I should just find a site online that can sell me exactly what I need. --- End quote --- I have attached a drawing of how I think the LED strip is wired. According to their picture, the big white objects on the strip are the LEDs and the little black objects are the current limit resistors. For individual LEDs the typical max current is 20mA with a voltage drop of 1V to 2V as a first guess in general terms without knowing the actual LED of interest. According to the link for the LED strip in your first post, each segment requires 9V to 14.8VDC with each three LED segment requiring 38mA. So, your 6 LED strip will use 76mA at 12V. Your 12V power supply will be sufficient for the LED and Arduino power conversion portions of your project. --- Quote ---MarkF, what tool did you use to draw your diagram? --- End quote --- I'm using DipTrace to draw my circuit diagrams and layout PCBs. Their FREE version is limited to 300 pins on the PCB (Which is a lot for small boards). You can request a Non-Profit license for FREE that increases the PCB to 500 pins. The PCB tool also has a nice 3D visualization of the PCB before you send it out to manufacture. Download the DipTrace 3.2 Freeware version from https://diptrace.com/download/download-diptrace/ |
| MarkF:
Be aware the most of my 12VDC wall-warts actually output 15V. |
| Youkai:
Ok lot of information there. I'll review later. I'm still a little confused about how to check if the power supply is isolated. Not quite sure what you mean by "DC output pin". I assume I need to use my multimeter to check for a circuit between each of the two prongs in the wall plug and some point on my breadboard. I'll try googling "check if power supply is isolated" or something similar to find a tutorial. Also yes I checked the voltage of my power supply and it actually runs at 17V. Good times. --- Quote from: MarkF on May 17, 2018, 01:49:09 pm ---I downloaded the spec sheet for a 2N3904 transistor: http://www.onsemi.com/pub/Collateral/2N3903-D.PDF --- End quote --- It looks like I cut it off in the picture but the asterisk on my package next to 2N3904 indicates that it has a "Different pinout". Looking at the diagram from the package (attached here again) it seems that the C and E are swapped on the BC547B (what I have) vs. the 2N3904 (your spec sheet). I attached a picture of the actual transistor if that helps. Just to triple check the cathode from the LED strip should go to the Collector of the transistor correct? If that's the case then that's the configuration that makes it very dim using the diagram on the package. If I turn it around so it's using the collector as described by your data sheet then it appears at normal brightness. Anyway thanks for all your responses. I'll do some testing and see what I can find. |
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