Self-melting Car Voltage Meter

this is a very simple but sometimes very so device it's a car voltage monitor or meter it measures the voltage in your car the voltage of your battery and Carmine's and displays it on this 3d display who is a classic multimeter you would have to open your car engine cover or hood or bonnet and measure the voltage directly on the battery who is this device it's much easier because you just stick it into your car cigarette lighters ahead and measure the voltage directly so you can easily keep the batteries running flat charging properly or even overcharging sometimes the car has a failure and it doesn't charge the battery now and sometimes it even over charges the tray recently I had a problem in my car because the voltage regulator fired and it was all charging the battery up to about 18 volts the battery was literally boiling and bubbling and almost all the light bulbs blew up just because of the stupid failure of this regulator inside the alternator if I had this device I would realize the problem much earlier it comes from eBay it cost me only one dollar 50 it's for both 12 and 24 volt cars and according to the listing the range of voltage measurement is from 8 volts to serve the rods so let's get using my bench power supply this one is the negative and the tip is the positive so let's try to calm the rock the job now it starts to wake up it shows something but still not very accurate and now it starts to be close to the ring value so from about 4 volts it starts to measure 5 point you now that you're at 6.2 with clothes not so bad nine point four okay twelve point nine fifteen point one okay eighteen point five good twenty three point something and let's go up to twenty eight it's close and let's go for thirty kind of okay at thirty volts it draws one hundred 10 milliamps so it dissipates three points three watts honestly the two crazy power consumption for a tiny voltmeter it's getting away hot and I can smell a bearing resistor so the device works but it draws a little bit too much power especially at higher voltages a 12 volt car has about 14 volts when the engine is running and this device will draw about forty three milliamps and dissipate 0.6 volts this is still kind of acceptable but a 24 volt car will have a good 28 volts with the engine running and this device will durable to ninety five milliamps and dissipate 2.66 valves and destroy a lot the maximum voltage of this voltmeter its articles at this voltage it draws 105 mallams and dissipates 3.15 works and get really crazy power so let's take a look inside and see you actually drawing so much power in it so how do i open it up okay unscrew this one yes there is the tape and in the fuse and with it the city under contact the negative one there to display with a filter a blue filter over a ready display that's a little strange within the few rules it is rated psyche arms are you crazy six amps for a tiny LED voltmeter I have no idea why did we use such a high value maybe the high current uses our cheaper dental current Ranas there's a penny board with a display one very big resistor another three resistors and a transistor and there is some chip under the display and that's it no SMD components this is not a transistor it's a PL four three one eye is an adjustable voltage reference and this resistor is probably what dissipates all the power but why what draws chaotic so here's the schematic and it's real simple there just to display the chip for resistors the voltage reference and of course the crazy fuse the voltage reference is connected at a simple eye with the reference pin connected directly to the kettle in this configuration it simply works as a 2.5 volt Zener diode so at this point there's 2.5 volts and because the supply voltage is up to 30 volts this resistor is dropping up to 27 point 5 volts in this condition the current through the resistor is I equals u over R and this is twenty seven point five volts divided by 270 ohms and this is zero point 100 you amps or 100 fumer arm the power dissipation of the resistor is T equals use I and this is twenty seven point five volts times zero point one hundred three ohms and this is two point eight watts and that's quite a lot of power this type of power supply is really inefficient and most of the power is being dissipated in this resistor just a small amount of power goes into the extra load the power supply the Zener diode is very inefficient because it drops the voltage on the register but also because it still draws the full current if the power supply is designed for 100 milliamps it will always draw 100 milliamps even if there is no Road even without any load the full current still flows through the resistor and the Zener diode and they dissipate all the power if you are drawing 10 milliamps from it it will still draw 100 milliamps because the remaining 90 milli amps are still going through the Zener diode this is exactly what's happening in this circuit and that's the reason why it's so inefficient it's much better to use something like seven eight oh five or lm317 let's say we are drawing 10 graphs again and this circuit will have a queston current of about five my arms so the total current will be 15 my arms and 16 milli amps versus 100 milliamps that's a big difference so a linear regulator is much better than a Zener diode because it would roll as current and also dissipated as heat this reference is working as a Zener diode here this is the stimuli sister this is the really display it's controlled in multiply X and it has no resistors so the current is only limited by the shape exam it in pin shape but it's hidden under to display and ever have to disorderly despite to see the marking there is a resistive divider going into some input and this is probably what measures the voltage that's another pain going to a 74 cases and there is a space for a capacitor on the board but it's all methylated I don't know what is the purpose of this one the voltage divider divides the voltage by 12 so when there is 30 Volt there will be 2.5 volt here so a deep maximum input voltage the voltage here will be equal to the supply voltage of the shape and there is one more pin on the chip connected to a pin or display and it's probably a jumper selecting the decimal point on the display there's absolutely no capacitor in the circuit I would expect at least a capacitor in parallel with each chip power supply I am running it at 50 involved for about 2 hours this is the maximum voltage wherever see another pod car and it's warming up but not so much and it doesn't failure now let's drive search the world after about half an hour 30 volts it's not horribly it gets extremely hot and the plastic is kind of warp a honestly that's crazy that's amazing and there is the resistor of course and Android Co disguised way the resistor is kind of melting into the display and user display is kind of soft now that's crazy take a look at the display this is just absolutely awesome after removing the Morton display the chip turns out to be this one I have no idea where it is so the conclusion is that is kind of okay in a squad car but definitely not in a thread before world car in a 24 volt car you can just plug it in read it and unplug it because definitely don't operated continuously in a third-world car it may be kind of okay but I still wouldn't write all the time because you never know and I would also change the original fuse to something more reasonable like 125 or 160 my arms this is diet involved and see you in my next videos

Channel: DiodeGoneWild

Views: 122,295

Keywords: Car, Voltage, Meter, test

Id: NDv4IvmvQWw

Length: 12min 15sec (735 seconds)

Published: Sun Apr 23 2017