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# johnsmith1212

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1. ## Practical use of voltage divider

hello, I am stuck with a dilemma which might or might not have a simple solution. more: giá chung cư 17 phạm hùng I have a psu supplying 46Vdc unofrtunately i need to step this down to several different voltages. 1) 14 to 20Vdc (best would be 16Vdc) to power a micro mainboard power supply thingy, using approx 100W 2) 12Vdc form as well a led strip, a fan, temperature sensors (LM35 i believe) and arduino atmega 2560 board 3) 5Vdc so i was thinking (maybe wrongly) to use a couple of 100W resistors in series (5KΩ - 5KΩ - 5KΩ&2KΩ - 2KΩ) and use it as voltage dividers. if I calculate correctly this should give me 2/19 * 46 = 4.8Vdc 5/19 * 46 = 12.1Vdc (2 times) 7/19 * 46 = 16.9Vdc more: giá căn hộ iris garden trần hữu dực so going from the assumption that all this above is correct, i started to wunder if the is a problem when there is a big difference in power consumption between the different voltages. as the 16.9Vdc "rail" would use approx 90-95 Watt (also pushing to the limits of the resistors used) and approx 1A for the 5Vdc "rail" if this is not a usable option.. is there an other way to do this correctly? i have a step down board but this one has a max. input power limit of 40Vdc, en even though i swapped the capacitors to larger once i believe that the actually limit is defined by (an) other component on the PCB, which i would blow up. specially as it would be on 24/7 also voltage regulators can supply this power.. any advice would be highly appreciated. more: giá căn hộ park residence lê văn lương ps: i understand i faultly use term rail here., and no a different PSU is not an option!
2. ## Scooter motor to power wood lathe

Hi! I'm new here so if this topic has already been covered or if it's in the wrong category, be gentle. more: can ho 17 pham hung I know enough about electronics to make me dangerous. I have a wood lathe and want to power it with a DC motor to be able to get better speed control. I have seen people use treadmill motors. I happen to have a few old 24 volt electric scooters (the larger kind with seat not the smaller stand-up only kind). I'd like to use that motor. I want to use AC to supply power to it. I'd like a speed control that goes from 0% to 100% and be able to reverse rotation. What is the best way to go about this? Can I use the controller and speed control from the scooter and power it with a transformer or DC power supply? Do I need to buy a different controller? more: can ho iris garden I don't have the specs for the scooters until I drag them out of storage (big job); I'm just looking for a general. You need to have a X big enough to supply Y with enough power kind of answer. Thanks!

4. ## Will the USB 3.0 cables get too hot?

Hello! This is my first electronic question. The image I have attached should be self-explanatory for a better understanding of my project. However, I need to know do I have to add any additional cable? more: iris garden trần hữu dực I am going to utilize 3 lap top computers (A, B, & C) and connected computer A to B with a USB 3.0 cable. Then I will also connect computer B to C with a USB 3.0 cable. I am going to access data from computer A with computer B. Then I will access data from computer B with computer C. I am utilizing MS Excel on all lab top computers. I will have all three lap top computers with the AC chargers plugged on. QUESTION: Will the USB 3.0 cables get too hot? If so, what cables should I use instead or what additional cables should I get? more: chung cu my dinh plaza 2 SPECS: Software: Microsoft Excel 2013 Hardware: 3 HP Pavilion lap top computer System: Windows 10 Network: The computers are NOT network...off line only more: chung cu eco dream nguyen xien Sincerely,
5. ## 150W LED streetlight....why dont they use the streetlight superstructure as heatsink?

Hello, The following below document (RDR-32) is for a 150W PFC’d LED streetlight. Its noticeable that the schematic on page 8 simply shows the earth connection being simply connected directly to the neutral. Surely this is not wise as RCD’s could be tripped? more: mỹ đình plaza 2 Surely for the sake of common mode noise mitigation, it would be best to have Y capacitors from live and neutral being connected to the earth connection? The schematic on page 8 shows no Y capacitors in the mains input section. Isn’t this a missed trick? Another point is that in a streetlight, the pole itself is earthed, and the streetlight head itself is inevitably metal and is directly fasted to the earthed pole. In other words, the metal casing of the streetlight head is also earthed. It surely makes sense, to use the metal head of the streetlight as a heatsink. –If one does not do this, then one has to isolate the metal head of the streetlight from the earthed pole, and surely this is a waste of time? more: chung cư pcc1 triều khúc Anyway, the RDR-32 document never speaks about using the earthed streetlight metal as a heatsink. Indeed, for the PFC stage, it recommends heatsinking the Boost FET and diode bridge to primary side DC bus ground. –Surely this is missing a trick?......i mean, you have a big chunky metal streetlight head, why haven’t they used it is a heatsink? Is it because they fear getting more common mode noise if they use an earthed heatsink for heatsinking the power switching FETs? Even then, surely it would be best to still use the earthed streetlight enclosure as a heatsink, and then just use a bigger common mode choke in order to mitigate the common mode noise problem? more: eco dream nguyễn xiển I mean, they have a big metal streetlight..why are they not using the streetlight superstructure itself as the heatsink?...i mean..it’s going to be there anyway. I appreciate that its earthed but earthed heatsinks are not at all uncommon.
6. ## Loud music from over-the-fence is causing offence...

After recently becoming somewhat broke, my wife and I were forced to settle in a small town in a very Wild-Westy part of New Zealand: Deepest darkest Southland. Like many of the inhabitants of this hillbilliyish community, our hard-smoking, hard-drinking, benefit-frauding 'neighbours' on the north side, are unable to function without a constant diet of loud 'music'. more: dự án eco dream (I use the term 'music' in the loosest possible way. It's just repetitive, thumping noise) I won't detail all of the hoops we've jumped through to try and get this racket to cease. Suffice to say we've exhausted almost all options, except, of course, moving elsewhere. We can't afford it. more: chung cư mỹ đình 2 However, it occurred to me that, as these trogs like their noise so much, it might be helpful if I were to amplify the waves that beam over the fence, and feed it back to them. I have a fairly powerful amp and a few spare speakers, but I'm sure I can cobble together something else if it's required. Advice will be appreciated. more: chung cư eco dream city
7. ## Sort of baffling what happened after a thunderstorm

hi would anyone know the answer to this . During a thunderstorm my girlfriend had breaker for the outlet for use near the sink OK the power surge tripped the breaker in the bathroom . She has a leaded glass night light that she puts there if nothing else is being used it has a switch on it . Well she told me in the morning that it was not working so i reset it Went to check to see if outlet was hot by plugging in the hair dryer IT WORKED THE Light STILL DID NOT . So i went to the kitchen with the bathroom stain glass light with the switch plugged it in it to my surprise it worked. WHEN i tried in the bathroom now it worked .COOL So works now my job is done. MY QUESTION IS why did this happen did something in the light have to be reset after the thunder storm or was it the outlet ?What was keeping the light from getting power and it was very low power one was a low wt bulb and a hairdryer would work that draws so much more worked well the whole time providing the power was on This is strange to me. Tags: chung cư pcc1 thanh xuân, eco dream
8. ## Popped SMD resistor, need advice for repair

Ill limit you with the boring details, but I have an electronic device that I can attach to my bike tire and it produces power and in return it can apply resistance to my wheel to simulate a steep hill or I must produce a certain number of watts. Its a great tool for training.... mehr: chung cư sun láng hạ I heard a pop and then took apart the unit to find a burned spot on the PCB. I later found the fried SMD melted to the inside of the plastic housing. Looking at everything, I found a part number for the replacement resistor and I plan on ordering that first. Ive never had to solder or mess with SMD parts before so I need advice on what to do, and what not to do. Im sure this was caused by an over-voltage, but Im extremely green, so if anyone can tell me what I should be checking out in addition to the resistor it would be greatly appreciated. Finally, what should I do about the hug burn on the PCB? Replacing the PCB is more than I have to spend, so I have to repair it. Recap: I burned a resistor off the pcb, I want to repair it, what else should be checked, how do I clean the huge burn? mehr lesen: toyota fortuner 2017, hyundai 1.9 tan Click this image to show the full-size ve
9. ## Why to calibrate strain gauges

Hi, I need to measure the strain in concrete beams. For this purpose I have purchased data acquisition system with a complementary 1/4 whetstone bridge circuit. The complementary circuit consists of 3 resistors of 120 ohm each. My strain gauge is 120 ohm and the gauge factor (k) is 2.11. The data acquisition system is modern and digital. Now, after connecting the strain gauge to the complementary circuit and exerts excitation (Ue) of 2.0 V (output) to the whetstone circuit and then loading the beam so that strain happens and the data acquisition system reads the voltage from the whetstone bridge (Ua)(input) that varies due to the strain in the strain gauge, my question is: Is it possible to use the formula: strain=4 Ua/(k . Ue) Why should I do calibration? and why the strain is not programmed to be calculated automatically to the above formula? The data acquisition system requests the k, Ue and the whetstone bridge type (1/4, 1/2, or full) so that it has all the necessary information for calculating the strain but will not work without calibration data!
10. ## Copper Clad Aluminum vs Oxygen Free Copper use, trade off, voltage drop in DC circuits

Hello! I recently got an Off-brand arduino kit as my first taste of electronics. It came with the board, components like LEDs resisters, breadboard, jumper wires etc... the problem is that when I try to plug some things into the breadboard, it rarely works. I struggle to plug anything in and when I do, I pretty much have to hope that I plugged it in right, have to check all the connections constantly and plug some of them half way to get it to work. the most I've been able to do is three flashing LEDs. It is so scetchy that if I bump the table a tiny bit, it stops working and I have to redo the entire thing. In a month, I will get a actual Genuino Starter Kit to replace this one. My question is, are good quality breadboards easier to work with. In every video I've seen, they pretty much just plug the electonics in and it instantly works. Is it really that simple, or more like the experience I already got? Tags: giá xe toyota fortuner 2017, xe tai 8 tan isuzu, giá xe toyota vios 2017
12. ## Power Supply from ViewSonic PC Monitor

Hi All My ViewSonic monitor quit working and I know it is many times a capacitor issue and in the ViewSonic case, in the power supply unit. I pulled the power supply and I can see various locations where capacitors/other components leaked. I posted a picture of what I found and have a few questions about the components. The arrow labeled "A" points to three components that appear to have leaked. What type of a component are they? The arrow labeled "B" (middle bottom up arrow) points to another light blue component. This is a capacitor, yes? The last arrow "C" points to the leakage in the area of the large capacitor and a light blue component. The capacitor looks fine with no "bulging" but the light blue component is not big enough to supplied that magnitude of spillage. Any comments on how to address the issue there? Finally, I am wondering if the magnitude of failure is worth trying to fix. A new monitor of this size is \$100-\$140. Thanks for helping me learn. Tags: hd700 đông lạnh, giá toyota vios 2017, hyundai hd72
13. ## Light switch does not seem to work, only 60V measured at the switch

I just bought a new house. On one wall in the kitchen is panel with 3 switches. I have know what 2 of the switches do (both are ceiling lights), but the third one does not seem to do anything at all. My first thought was that it controlled one of the outlets in the kitchen or family room right next to the kitchen, but after taking a small lamp around to every outlet that I could find I could not identify what the switch was for. During my testing, every outlet tested had power and lit up the lamp ( I did not test the voltage at the outlets, though). So the next thing I did was take the cover plate off the switch panel and tested the voltage going to the switch in question. I tested by touching the wires going into the switch without removing them from the switch. With the switch in the on position I got zero voltage (Actually it was 0.016V), but when I put the switch in the off position I got 60.2V. I am not an electrician so I have no idea what this means. I do know that there are different types of switches (2-way and 3-way) and the one in question is a standard single switch. Now while I was checking the Voltage I did notice that some of the plastic body of the switch was cracked and broken and some of the material was actually missing. So I guess I have a couple of questions: 1. What would cause the voltage to only be 60.2V? 2. Could the broken material on the switch be causing what I am seeing? 3. How can I possibly determine what this switch is supposed to control? This is of course a very hard question for folks to answer but I am hoping maybe there is some trick for figuring this out. I am just worried that there may be some 'hidden' problem in the walls. Don't want an electrical fire. Thank you for any help you can give me. Tags: gia xe yaris 2017, hyundai hd700 đồng vàng, giá toyota camry 2016
14. ## Harman Kardon AVR 147, Relay doesn't switch on.

Hello, Yesterday I was watching a movie, and my HK AVR 147 just stopped working, and I could heard the relay switching off. I turn off the amplifier, and turn it on after 2 minutes, and it started to work for about a couple of seconds, and stopped again (again with a relay noise). Now, it doesn't work at all. I power the amplifier, it stays on standby (amber color). When I hit the button to start the amplifier, it turns blue, but with no relay switching noise. After 10 seconds, it returns automaticaly to Standby mode, with the amber color. Could anyone help me on this matter? I already checked the fuse, and it's OK. Tags: giá xe hd700, toyota altis 2016, xe hyundai hd72
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