I'm building a simple voltage regulating circuit with LM317T and two reistors (330r and 68r), im using a breadboard
when i build the circuit i have a 1.5V output (middle Pin) from it, which is what i want but when i put a load from the output to 0v the load only has a Vd of 0.6v
it makes me think there is a resistance im missing somewhere between the output and 0v but the load is the only resistance i can see, does the breadboard have a high resistance?
i have a load between the middle pin and the negative channel on the left (the same one as the resistor)
What is your input voltage?
In the LM317 datasheet is graph showing the minimum input voltage for various load currents, you will need something like 1.5 to 2.5 volts more on the input than the output.
im not sure, but i think this is where the problem lies, it has a very small resistance so the current is going to be way to high for the LM, ill have a mess when im home and let you know how i get on
im not sure, but i think this is where the problem lies, it has a very small resistance so the current is going to be way to high for the LM, ill have a mess when im home and let you know how i get on
Probably also temperature issues. Keep in mind, you can't draw anywhere near the max current without a heatsink. And if you try, it has built in thermal shutdown so you gotta do your calcs.
Lets just say you're trying to pull 1A. Means the power dissipation in the regulator is (6-1.5)*1=4.5W
Thermal resistance junc-ambient is 80degC/W. So that means at 1A, you're heating to 360degC. Which will obviously trigger the thermal shutdown.
The current without a heatsink you can actually draw is more around 260mA, or 6Ω. That'll keep your junction temp at max 100degC (which is still a lot!).
Calcs:
P=(6-1.5)*260mA)=1.17W
JuncTemp=1.17*80=93.6degC
ye :/ didnt even think of this, im thinking of using a power resistor instead between the 6v and the load but now im thinking is the battery going to last with 10A being drawn :/
the load will only be used for about 30 seconds but its running from 4 AA alkaline Bats
ye :/ didnt even think of this, im thinking of using a power resistor instead between the 6v and the load but now im thinking is the battery going to last with 10A being drawn :/
the load will only be used for about 30 seconds but its running from 4 AA alkaline Bats
my problem is i need my circuit to run on 6v but one branch of it can only work at 1.5v, the load in this branch has a very low resistance so the current will be very high about 10A i was looking for a way to drop the 6v to 1.5v
i cant add aother resistor as this would drop some of the voltage and my load wouldnt have the 1.5v it needs,
my problem is i need my circuit to run on 6v but one branch of it can only work at 1.5v, the load in this branch has a very low resistance so the current will be very high about 10A i was looking for a way to drop the 6v to 1.5v
i cant add aother resistor as this would drop some of the voltage and my load wouldnt have the 1.5v it needs,
i have a 6v power supply on a circuit, in a different circuit i have a glow plug rated at 1.5v, the glow plug has a resitance of 0.15ohms, i want to use the 6v power supply to power my glow plug, how do i get to the needed 1.5v from the 6v source. if i use a resistor to drop 4.5v in series with my glow plug then the total resistance is 0.6 ohms, giving me a current of about 10Amps
i have a 6v power supply on a circuit, in a different circuit i have a glow plug rated at 1.5v, the glow plug has a resitance of 0.15ohms, i want to use the 6v power supply to power my glow plug, how do i get to the needed 1.5v from the 6v source. if i use a resistor to drop 4.5v in series with my glow plug then the total resistance is 0.6 ohms, giving me a current of about 10Amps
Yeah, I'm also being a quite naiive about what a glowplug actually is, haha. But man, 10A, are you sure thats what it needs? I know its rated at 1.5V and a resistance of 0.15, but are you sure it wont work at a lower voltage/current? 10A is obscene.
i did think this myself but after doing a bit of research apparently thats pretty normal, a glow plug is a a coil of wire in an engine to warm it up before the 'burning' of the fuel so it does get pretty hot, i know it needs 1.5v as the manual states it and i measured the resistance myself so i assume it needs the 10A, after looking online again i saw some glow plugs need up to 50 amps :O pretty unbelieveable really in a car (side tracking here) haha
i have a 6v power supply on a circuit, in a different circuit i have a glow plug rated at 1.5v, the glow plug has a resitance of 0.15ohms, i want to use the 6v power supply to power my glow plug, how do i get to the needed 1.5v from the 6v source. if i use a resistor to drop 4.5v in series with my glow plug then the total resistance is 0.6 ohms, giving me a current of about 10Amps
That's because the glowplug takes 10 amps (according to it's voltage and resistance ratings) , use the correct 1.5V battery - or make toast if you're adding a resistor to 6V.
can i not use a power resistor of about 50w, i could go out and buy a 1.5v battery to do this seperately or even a starter but i wanted to try a few things, learn a few things aswell, if its impossible ill admit defeat but i would of thaught there was a way somehow
ye :/ didnt even think of this, im thinking of using a power resistor instead between the 6v and the load but now im thinking is the battery going to last with 10A being drawn :/
the load will only be used for about 30 seconds but its running from 4 AA alkaline Bats