| Electronics > Projects, Designs, and Technical Stuff |
| Borderlands style jewelry box research thread |
| << < (12/17) > >> |
| Youkai:
1) Don't the decoupling caps you are recommending and the 1000uF capacitor already there do the same thing? Is this just an extra layer of smoothing or is there some other purpose? 2) When you say 0.1uF but more is better; what does "More is better" mean? Is there some upper limit to how much is reasonable? I found this 0.33uF cap on jameco: https://www.jameco.com/z/MD-33-Capacitor-Monolithic-Ceramic-0-33-micro-F-50V-plusmn-20-37-_138237.html Is that enough-more to be better-enough? 3) What is the purpose of sensing the 9V and shutting off the pins? I assume (based on previous posts) that I can not power the whole circuit via USB (while programming). At most I would plug in 2 other components while programming it and the servo will never have a load applied to it while programming. So I would think USB could handle that ok. My plan is to use the Arduino while writing the program since it has a 5v output pin that I could use to power a single component while getting the code correct. Then I would only ever wire up the pro-micro/whole-circuit using the wall wart so there would never me a time when all of the components are attached and the 9V isn't present. Is it an issue if my Arduino is sending commands to a NeoPixel that isn't there? Oh reading your last sentence again I might see it. I remember reading on the Adafruit guide that you want to power the pixels before the micro-controller. So I guess you can somehow brick the pixel if you send an update command to it when it's not fully powered? Cool >.> 4) I think I put the new Schottkys in there the way you explained but I don't see how they help with anything. I understand that if the Pixel gets a data input when it is not powered that can cause a problem but I don't see how the diodes somehow prevent the signal from getting through when not powered. I don't see how the ground connected one does anything ever under any condition. And If the positive rail is connected to power then nothing from data is going through because the Voltages will match right? Thus the signal goes to data; perfect. If it's not powered it's a wire with no connection at the end so there is no circuit so thus now power will go through the diode anyway right? Or does one of the capacitors somehow allow a circuit to complete and "eat" the signal? 5) Question about actually soldering this together. Maybe this is complex enough that it makes sense to use a Perfboard. If I don't what's the best way to do something like the 5V Reservoir Rail connection where I have 5 wires connected. Would I expose enough of each that I could twist them all together in one group and solder that together; or perhaps expose a lot of one of the wires and solder the other 4 to unique points along it? 6) New diagram attached. I think I got the Schottkys in there correctly as it seems if they were the other way it would cause issues. Though can you confirm the attachment points are ok. Do I actually need to go to the 5V rail on the upper ones; or is connecting the 5V and Data pins using the diode ok? They should be effectively the same right; with the exception that if I go back to the 5V rail that puts a capacitor in the circuit that wouldn't be otherwise? |
| Ian.M:
1 & 2. The 1000uF electrolytic capacitors have a fairly high impedance at high frequencies due to their size and wound foil construction. A 0.1uF or 1uF ceramic has a much lower impedance at high frequencies so you need both in parallel, with the ceramic as close as possible to the load that will be drawing pulses of current. You don't need one for the Arduino as it already has some on-board. 3. The Neopixels could be damaged if data is applied without power. If the 9V is missing its preferable to stop and not do anything (except possibly blink the Arduino's on-board LED to indicate its waiting for 9V power), so that's why I recommend sensing the 9V in. If you want to test the board while its hooked up to your PC by USB, supply 9V as well. 4. For the DIN protection Schottky diodes, use low current ones. If you are building it using SMD parts BAT54S would be very suitable as it gives you two series connected diodes in a single three pin SOT-23 package. If you are using through hole parts, BAT43 wuld be suitable. Ideally solder the DIN protection Schottkys direct to the Neopixel LED strips, as there they can protect against loose power or ground wiring. If you mount them on your main board, they should go as directly as possible to the Neopixel connector pins. 5. I'd build it on Veroboard, with the Arduino soldered down and a full width set of strips for the 5V rails and the Gnd rail just beyond the end of the Arduino to mount the big caps and big Schottky to. 6. Your new diagram looks good. Ceramic decoupling and DIN protection Schottkys should be as close as possible to the Neopixels - ideally soldered direct to the strips, otherwise at the three pin connectors for the neopixels on your main board. |
| Youkai:
I like the idea of the BAT54S. If I'm interpreting the spec correctly: https://www.mouser.com/datasheet/2/308/BAT54S-1118484.pdf Data goes to pin 1 +5V goes to pin 2 GND goes to pin 3 Is that correct? Then I just solder the pins on the BAT45S using as short a wire as close as possible to the pins for the Pixels? EDIT: note that the Pixels are going to be in a different physcial location than the board. So I'll have a few components that aren't attached to the board. Specifically anything that needs to be connected as close to the Pixels as possible. I suppose there could be seperate little mini-boards for the pixels. That probably makes the most sense. |
| Ian.M:
Yes. You could superglue the BAT54S direct to the back of the Neopixel strip, and hook it up with individual strands of tinned copper wire, or you could solder it to a scrap of one pad per hole matrix board the width of the neopixel PCB, and put the bare ends of the wires through that then on to the neopixel PCB pads. |
| Youkai:
Ok I have updated the diagram to have the BAT54S in there. I also added the voltage divider for pin 1 to sense 9v. Is that wired correctly? I got my neopixels in the mail today and noticed they have two ground connections. If you look at the last image you can see it: https://www.adafruit.com/product/2869 But the images showing them working only have 3 wires connected. I can't find any information about why there are two ground connections. Do I just use the one on the same side as the images from the site? I assume the second one is redundant for some kind of extra safety but not needed? I think it's pretty darn close at this point. Time to start figuring out what I'm missing and order parts. EDIT: I was re-reading the posts some more and saw your comment about the Bat43 for throughole. I'm not really planning on using a board at the LED panels; or if so it will be as small as possible. Is it ok to solder the BAT54S to a board? I'd like to use that because some of the wiring is already done for me and it's harder to mess up (i.e. get the polarity backward). |
| Navigation |
| Message Index |
| Next page |
| Previous page |