Posts posted by mumcs01
This is fantastic! Thanks again!
Great explanation! Thank you Very much!!!!
I've done a few projects making my own PCB using standard mil traces, but overall have never concerned myself too much with trace size because everything I was doing was low current/voltage.
Well I've kind of crossed that line, and I've built up a project that is tripping a 120VAC relay (NC side, not coil... Coil is 5VDC), and the device I'm powering off of this relay has the potential of 900Watts.. So potentially 7-8 amps. The relay and the terminal block that I'm feeding the device off of are rated far beyond this (10Amps), but by question is, is there a chart or guide or article anywhere that approaches the limits of trace size (like the limits of wire size). My relay and terminal block are PCB mount, and I really would like to keep everything on one board instead of running leads places.
Any input would be great. Thanks,
Thanks for the response!
To take this one step further, do you know what constitutes a devices that operates with current or voltage dependancies? A Relay is voltage dependant and requires a current. I'm assuming this is because it has a resistive coil? An LED (Diode) is not generally resistive? Am I on the write track here? A transistor relies on current at the base... What about a simple light bulb? It needs a specific voltage, but as for current, it will draw what it needs... So a voltage divider would be used in this case.
I guess I'm asking what is the sign or test to determine what is a current based device and what is a voltage based device.
I'm trying to nail down some theory here, that is for some reason fuzzy, even after a ton of reading. Thanks again!
HI! I have a theory question I have been trying to wrap my head around for a while about voltage divider formula. Anyone that can help clarify this for me? I've tried finding the answer seaching around for weeks now.......
Can someone explain the pro/cons of using the LED Voltage drop formula for dropping a Voltage for an LED, compared to using a voltage divider circuit via 2 resistors? Example. 5VDC with a standard LED, you'd (5-2)/.020=150Ohm resistor does the job to give you about 2V @ .020 via the LED Drop formula. Why use this method compared to a 2 resistor voltage divider to do it? Does it matter? Its something I've never gotten a straight answer on. If both work, is there an advantage/ disadvantage to either design?
To take this further, Lets say your using a mythical device that requires 80mA @ 8VDC and a 30mA @ 5VDC device off of a single 12V 600mA rail.... With the supply of 12V, would it be sain to feed both of these devices off of the 12V rail (coming off in parallel) using the same LED formula?. So for the 80mA @8VDC device you would use (12-8)/.080=50Ohm Drop resistor to the device, and for the 5VDC @30mA you would (12-5)/.030=230Ohm.... OR should you use a voltage divider? Why? These are mythical devices... Just find of random to prove the point of requiring different voltages to different devices off the same primary
Thanks in advance!
Membrane switches and Screened overlays
in Datasheet/Parts requests
So there are tons of ways to make professional looking PCBs these days, which make the inside of projects look pretty, but I'm looking for a way to make the outside look good on a budget. Heres what I'm looking for and maybe someone knows a source. I have a small project I've made that I'm looking to make an overlay for in plastic. It requires a clear area for an LCD screen and 4 input buttons. There are two ways I could go about this, with a plastic overlay with buttons protruding, or an otherlay with 4 membrane switches in it. I'd go either way.
I've done a lot of searching and found a number of production houses which will do both, but they are into volume orders. To be honest this project is a personal invention I'm just trying to make look good, but I have another I may want this for as well, but I'd be looking at a few dozen, not thousands like most production houses are looking for.
Does anyway know of either a homemade way of doing this, or a low volume production house (Like ExpressPCB is for boards) to do this.....