New answers tagged

0

Car batteries are starting batteries - their internal resistance is low since approx., 450 amps (for petrol engines) and 800 amps (diesel) and even more need to flow to start the engine. Internal resistance goes up (high) with age and use - eventually even if the battery goes up to a decent 12.5 volts, it may still not charge enough due to high resistance ...


6

A short story Long before solid-state electronics and vacuum tube electronics, lead acid batteries were and are the longest living battery technology. Being a multiple of 2V +/- 0.1 per cell or 2.36V on float charge or 14.2V, the 12V battery was not the 1st common voltage for cars. Initially it was 6V but as gas engines grew , they used 2x 6V batteries ...


2

There is no guaranteed correct answer, but the "nominally 12V" available from 6 x lead acid cells and its adoption as the standard for most domestic motor vehicles is a powerful force in setting a standard in other areas. Some early cars used 6V, which proved far from ideal, and larger non-domestic vehicles use 24V (as Tony noted). But for many purposes "12V ...


1

I don't see how it can even work to begin with. Based on the schematics, the AVR is completely missing the AVCC power supply connection. And lack of proper bypass capacitors at AVR supply pins can cause problems too.


1

The circuit worked all fine until 7805 was moved a bit by jerk and all becomes hell, atmega stops. Is it permanent damage? I am unable to understand what is it and my money is wasted on buying new chips and demoralizing me to continue. 'Jerking' the regulator should not have any effect, unless one or more pins has a poor connection. If the GND pin ...


3

I noticed is a "jerk" to 7805 did it Any interruption in the 7805's ground connection would result in the 12v input being applied to the downstream circuitry, resulting in immediate damage. You really need to arrange things such that a "jerk to the 7805" is not possible, ie, solder the connection or use a good connector in a way that it is not under ...


2

The zener diode is connected the wrong way. Instead of being in series with the atmega it has to be in parallel, with the cathode connected to 5V and the anode connected to ground. In your case you don't really need a zener diode, because the 7805's voltage should be pretty stable (linear regulator) and I would say "paranoia" is not an argument ;). That ...


0

The fuse is there to protect your cables. The problem that you have is that the maximum current is taken by your 3kW inverter (3000/12). This figure probably exceeds the "ampacity" or maximum current for 75mm squared cable. You need to increase your cable size to cope with the inverter current and then fit a fuse at or just above the ampacity of your ...


1

I realize this is an old question. I decided to answer it anyway. OP is probably gone but others may benefit. Fuse size cannot be discussed without discussing wire size. The purpose of the fuse is to prevent wiring from getting too hot. If the wire gets too hot it may cause burns to people who touch it or even cause the insulation to smoulder or burn. It ...


0

Most AC-to-DC power supplies have no problem when being back-fed with voltage that is less than or equal to the normal output voltage of the supply. This feature is often used when putting two identical DC power supplies in parallel so as to have redundancy. The problem that you are having strongly suggests that the 5V power supply is wired backwards to the ...


Top 50 recent answers are included