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26 Threads found on 7805 Switching
The 78M05 limits its output current to only 500mA. Use a normal 7805 that limits 3 times higher.
Dear Friends , I would like to know what is the best way to drive the contactors for switching on/off motors using mcu , optocoupler etc. Recently i tried to drive 2 contactors using 2 relays driven by the mcu.The description of ckt is as follows : 2 windings from transformer : a.)0-9 & b.)0 -14. a.) Driving the 7805 regulator for running m
I am switching an AC 230V solendoid on and off using a relAy to drain a tank of water. The problem is when the solenoid turns off I get a large spikes on the output of by 7805 reg. The nuetral is permanently connected to the solenoid with the relay contact switching the Live . Anyone got any ideas of how to suppriss the noise spikes?
Hi Dynamag and welcome to EDABoard, For measuring You can use Hall sensor ACS712, A1302, or any other similar. Power supply for circuit should be done using switching tech, 7812, 7805 is linear and will make some power loss according to circuit design and needs. Best regards, Peter
A 7805 will NOT work in this case. The input voltage at 6.5V is too low for it to operate. If you use a linear regulator you will produce heat - I'm afraid that's physics and there's nothing we can do about it. The best solution is a small switch mode regulator like the MC34063 as tpetar suggested. It's only 8 components instead of 3 and none o
Use bridge rectifier at transformer secondary like W02G. The use of 7805 is not necessary and its output will be 5V not 3V. Also, its efficiency is less than 60%, u will end up wasting power but it will cost less and good for testing purposes, instead use switching buck regulator, it will give efficiency of 98%, and advisable to use in applications
Keeping in mind the large voltage gap between input and output, the power dissipation in the 7812 as well as the fact that the only purpose of the 7812 is to reduce the voltage gap for the 7805, you could use a switching regulator here to provide the 5V instead of the 7805, and you won't need the 7812 at all. With efficiency > 70% (common of (...)
For "converting" voltages as high as 30V to 5V, to be used for power sources, you could use switching regulators instead of 7805 to maximize efficiency and minimize power loss and heat. There are many such switching regulators available. You may take a look at L4971 and LM2575 among others. L4971:
The 7805 can be configured as a switching regulator. Look at the datasheet. Another option although a bit expensive
Why the 7805 is called as linear regulator and what are the difference between the switching and linear regulators...
i made a circuit, in which graphic lcd interfaced with controlller 8051.. and the problem is that the 7805 heats very fast and i also attached heatsink with it, bt the same problem occur.. will u find the fault?
hi; i am using 7805 and 7812 in my circuit. the DC input voltage out of Bridge and Capacitor is 40V DC but the maximum input voltage range is 35V for 78xx series. when i connect voltage divider circuit to apply 9V at the input of 7805; The voltage divider circuit normally shown 9V but when i connect that node of voltage divider network to th
If you need 5 volts at the output, why do you have the zener and the 1n4007 after the 7805? Get rid of these two, and you should have your 5 volts.
regards! i am currently using 7805 regulator for 12v ac converted todc and then fed to 7805, i have a microocntroller avr Atmega8, and a uln, amax485 and atleast 3-4 leds that are constantly on .... hence the regulator gets too hot... i want to replace it by a swithing regulator... one option for me is [URL="shop.tux
whenever i connect 8 ir sensors(for line tracing) to LM7805,it gets heated up in no time.. i tried using a heatsink.. but the heatsink also gets heated up.. i supplied 12v to 7805.. can anyone suggest a solution for reducing the heat dissipation from 7805?? try to using switching like this [url=www.nomad.e
Hi, I am using an Onsemi MC33269TG voltage regulator as a constant current source to charge a pack of NiMh batteries (12V). I found that on switching off the circuit's input the battery pack powered the circuit back by providing current through the voltage regulator to the relay, then to the 7805 and to the pic,etc. To prevent this back flow of
Hi, 1300ma at 5V seems a very high current for a web cam - is it fitted with uv lights etc ? Think you need to check its actual current with a meter You need a simple voltage regulator like a 7805 max 1amp or LM323 max 3amp. Choose your regulator so the actual current from it is no more than 50 to 60% of the maximum to ensure good life.
for getting 5V DC and 1A current the best thing is LM7805 or simply 7805 use a transformer of rating 0-12V 1A use a rectifier ckt use a filter capacitor and 7805 you will get 5V dc with max o/p current of 1A
Use a big enough heatsink, 7805 has a thermal protection and is shut down when the temperature is to high. For bigger current you may use an external transistor. The best solution to minimize power dissipation is a switching regulator like this: www.national
Hi drbizzarow, Any linear regulator (such as PQ30RV31) will get just as hot as your original 7805 design. To reduce power dissipation (heat), you must use a switching regulator, as suggested by several folks above. Possibly helpful: National Semiconductor has an on-line tool for designing and simulating power supplies, and for buying a kit of