I'm making my own PCB for atmega and till i solder everything i start testing the 5v regulator
That's my electronics for 5v regulator found it online, I should of have 10uF 35v caps but seller
gave me wrong ones 10uF 50v but i don't think it's a big problem.
What's happening is I put a 12v battery as Input and as output a 5mm led and a digital voltmeter
to see exactly how much voltage gets on the output, the voltage is from 5,2v ~ 5.5v but the real problem
is the linear regulator heats up really fast I don't have a temperature meter but just by touching i can't hold my finger for long time it's getting hot really fast.
So what could be the problem? My 5v reg. circuit is not good?
I should of have 10uF 35v caps but seller gave me wrong ones 10uF 50v but i don't think it's a big problem.
No problem. The voltage rating on a capacitor is the maximum you should apply.
as output a 5mm led
Do you have a resistor in series with the LED?
voltage is from 5,2v ~ 5.5v but the real problem is the linear regulator heats up really fast
The voltage shouldn't be varying that much.* And, if the load or input voltage isnt' varying, the output should be rock steady. And, the regulator shouldn't be getting hot with just an LED load (as long as you have the resistor to limit the current).
You may need a different type of capacitor (i.e. ceramic capacitors). Electrolytic capacitors don't "act like" capacitors at high frequencies. Ideally, there are no high frequencies in your DC power supply but the capacitors are there to prevent high-frequency oscillation.
The LM7805 datasheet shows a 0.33uF cap on the input and a 0.1uF on the output. These should be mounted close to the regulator chip. There is no harm in leaving your 10uF capacitors there also (and there may be advantages to leaving them.
The datasheet says between 4.75 and 5.25V. But in my experience, these things are usually more than 4.9V and less than 5.1V.
The regulator gets hot because it dissipates power as heat.
Yea but it's just a led 20mA.
Do you have a resistor in series with the LED?
I don't ofc i should of put a 100ohm one.
Ok I understand that get hot " because it dissipates power as heat " but it's kinds too hot, there is a metal on the regulator so i didn't thought that it gonna heat up so fast and hot. Using my pcb i may draw more than 500mA if i add extra components.
Btw what's the minimum voltage input for that regulator?
Really funny, i just tested again the 5v reg. and added a 150Ohm resistor with the led and the reg. is normal warm not hot.
Btw as I am here and talking about the regulators. I tried to buy a LM1117T 3.3v but the seller game me a KIA 1117BP 3.3v what's the difference? and I tried the same circuit replacing the 5v reg with the 3.3v reg and the regulator got really hot (without the led just a voltmetre at the output) and no readings of voltage. Why that happend?
What I find strange is that your LED didn't die without the resistor???
LEDs are current driven devices (given the proper minimum voltage) - meaning that unless you control the current (ie - with a resistor in the simple case) - it will take as much current as the source can supply.
The 7805 being a linear regulator, dumps the voltage difference as heat - so in this case, the LED was being seen as essentially a dead short across the regulator; it's dumping (or trying) to dump 7 - 10+ watts (7 x 1.0 or 1.5) as heat!
Without a properly sized and cooled heatsink mounted on the metal tab, that regulator won't last long; it's possible that you may have already damaged it - or maybe not - the 7805 is a pretty robust device, and you may not have let it run long enough to cook itself (you'd probably only be able to notice the damage by running a test circuit from the datasheet under controlled conditions, plotting the output, and comparing it to the datasheet's graphs).
Again, though - I am curious as to how your LED survived all the experimentation you did prior to adding the resistor...
(might need to edit that, forum is messing up the beginning)
KIA is some other brand www.ceted.org/engineer/KIA1117.pdf
Check the pinout between them, see if they are both the same.
it's possible that you may have already damaged it - or maybe not
I've seen people saying that 5v reg. has a safe system turning off after high temperature also i've seen this
on youtube video after 130 Deg. C` the reg turns off and gets back on after cools down under the estimated temp.
I am curious as to how your LED survived all the experimentation you did prior to adding the resistor...
(the led is blue)
At the begging i was like ok it's just a test so im not gonna add a resistor so the led started to flash in strange colors like a rbg led, colors like (violet) i was like wth is going on and didn't payed more atention at it so after the few above comments i was like ok so the missing resistor was the problem (of fast heat).
Btw can someone answer me about the :
Btw as I am here and talking about the regulators. I tried to buy a LM1117T 3.3v but the seller game me a KIA 1117BP 3.3v what's the difference? and I tried the same circuit replacing the 5v reg with the 3.3v reg and the regulator got really hot (without the led just a voltmetre at the output) and no readings of voltage. Why that happend?
I just replace the 7805 with the 1117 and the 1117 start heat up really fast like 2~3sec and it's above 100C`
not sure why is doing that but i observed when i put and unplug really fast the 1117 the led blinks and i got a 12v reading on the outpu. What's wrong?
The functional block diagram might be the same, the physical connections are not.
On 1117, the pins from left to right are Gnd-Output-Input. The tab is the output also.
On 78035, the pins are Input-Gnd-Output. The tab is Gnd also.
On 1117, the pins from left to right are Gnd-Output-Input. The tab is the output also.
Facepalm, is there other 3.3v reg with the same diagram and same pin with the 7805? I already made a circuit
based on that diagram and I don't wanna to be wasted.
That means you should be running 20mA through it. With no resistor, you are running a lot more current through it.
Ohm's Law says: Current = Voltage/Resistance. Current depends on voltage and resistance... More voltage = more current. More resistance = less current.
Ohm's Law is ALWAYS TRUE, but it's tricky with LEDs. LEDs are non-linear (like all diodes). That means the resistance changes when the voltage changes. When you go above the diode's "breakdown voltage", resistance drops to almost zero and you get lots of current (if there's nothing to limit the current).
Ok I understand that get hot " because it dissipates power as heat " but it's kinds too hot, there is a metal on the regulator so i didn't thought that it gonna heat up so fast and hot. Using my pcb i may draw more than 500mA if i add extra components.
A 7805 will heat up really fast and get really hot when they are wired up backwards.
I didn't connected anything backwards on the 5v regulator, the regulator got hot because i didn't put a resistor between the led and the regulator. What got really hot is the KIA 1117 3.3v regulator and not sure why.
ofc i should of put a 100ohm one.
