A:How can I tell which component on a pcb is the fuse?
I am looking at an lcd inverter and trying to work out which part I need to replace to get it working again. Problem is that all the components look the same. I am trying to work out which is the fuse, but all the components on the pcb are coloured, rectangular devices with numbers on, and no indication as to which is a fuse.
Is there a way to tell which is the fuse, and an easy way to recognise transistors and other components?
Do you know a good site for help me?
Q:
I'm not sure what you are looking at, but those rectangular things are most likely integrated circuits. And they are probably surface soldered to the board.
The fuse should be marked on the board with some kind of identifier such as "F1" or F-1 or something like that. If it is a serviceable part at all it will be cylindrical with a wire or lead out each end and go through the board. If you have no components that go thru the board then you have an SMT type board and you are not equipped to fix this at home unless you are very talented and experienced in surface soldering.
Companies spend lots of money on such equipment (millions) so you are probably not going to be able to change any fuses. AND there are SMT fuses as well. There are so many different ways these could be identified someone with experience like me would have to spend considerable time looking at it to figure it out.
Is it really worth the aggravation to fix yourself? Perhaps taking it to a shop, if it is worth it at all.
A:What is the relationship between the track width in a PCB and maximum current that can pass through it?
for example a PCB track with 1mm tickness can not pass 40A direct current.
Please give me a formula or a table to calculate the track width according to maximum current can pass through it.
Q:
First look up the resistivity of copper.
Measure the length of the track needed.
Now calculate the cross section of the track you propose to use.
Now work out the resistance of the track over its length.
Now calculate the voltage drop at the current you propose it needs to carry.
Now calculate the power dissipation in the track. Now, using metallurgical data, calculate the temperature increase in the track.
Decide if you are happy at that temperature.
If not, the power dissipation will decrease by half by doubling the width of the track (provided the current is the same).
Or you can do it the easy way. Ie, use a wire bridge thick enough to handle the current you require.
A:How I can identify negative sides and positive sides in PCB?
I have remote control for car (rc toy) and I want to know how I determine positive side & negative side of pcb for each button (left , right, backword & forward) in remote
Q:
You need to get a DMM, a digital multimeter. Set it for dc voltage, put black lead on negative side of battery, then check the trace on each side of each button, with the button in normal position and when actuated. Watching the voltages on each lead will show you what it is doing, and help you to draw the schematic.
PC boards do have two sides, but they are not identified as pos and neg.
For a through hole PC board, usually the side with the silk screen (printing) on it is the side where the components are mounted, with the other side the one that is wave soldered.
A:What is the best way to dispose of used ferric chloride PCB etchant?
I know of at least one method, diluting it and slowly pouring into the drain, but it can still stain and eat away metals in the pipes a bit. Is there something else I could use to possibly just "neutralize" it? I think an alkaline metal nitrate would work (Li;Na;K) or some other salt. That or maybe even just try to get the pH as neutral as possible.PCB is an acronym electrical engineers/hobbyists etc used to stand for PC-board, a.k.a Copper-clad board.
I also now realize a nitrate salt, as well as many other salts, would only form complex ions/ligands. Especially since the used ferric chloride would already contain complex ions due to the copper dissolved off the board (copper and chlorine like to do that a lot). Although, even that might bring the pH closer to 7.
Q:
PCB enchant is Ferric Chloride (as you said), with a chemical formula of FeCl3...Iron (III) Chloride.
When you pour the Iron (III) Chloride on to a Copper-clad computer board with your circuit traced out on it, the enchant will eat away the undesired Copper by Oxidizing it to the very soluble CuCl2 and reducing the FeCl3 to FeCl2.
After you use your enchant, you will have a solution of FeCl2, CuCl2, and probably some remaining FeCl3.
All of these can be removed from solution by precipitating the metal ions out using a Hydroxide.
All of the Iron/Copper Chloride salts in your used etchant solution are quite soluble, but their Hydroxides are barely soluble.
if you add some Sodium Hydroxide ('lye', commonly found in drain cleaner), you can form the metal Hydroxide precipitates which can be filtered or decanted off, leaving a much milder solution behind.
FeCl3 (aq) + 3 NaOH (aq) --> Fe(OH)3 (s) + 3 NCl (aq)
FeCl2 (aq) + 2 NaOH (aq) --> Fe(OH)2 (s) + 2 NaCl (aq)
CuCl2 (aq) + 2 NaOH (aq) --> Cu(OH)2 (s) + 2 NaCl (aq)
Make sure and dilute the solution before you add the NaOH (preferably a NaOH solution). Dissolving NaOH in water is a very exothermic process, so the solution’s temperature will rapidly rise if you are not careful. It is also a very bad idea to get any NaOH in your eyes or on your skin, so be careful but when used responsibly NaOH is fine.
When the Hydroxide precipitates are heated, they will form the metal Oxide salts. So for example, by heating Cu(OH)2, you will form CuO. The heat generated by the above reactions might also be enough to convert the Hydroxides into Oxides, so that is certainly a possibility but disposing of Fe2O3, FeO (or the combination of the two, Fe3O4), and CuO should be no problem.
The remaining NaCl solution will be no problem disposing of down the drain, as would any excess NaOH which happens to remain. |
