i'm running a stepper motor with a supply from LM7805 , my problem is the stepper draws more than 1.3 A , so the regulator goes so hot in a few seconds ,
i need to use another regulator LM too , but can stand this high current ,
i know the 138, 338 ..... i don't like them they are variable , i need a constant one like the 7805 and high current
Only you know why you're using a part unsuitable for the task. You should try to overdesign. If your input power is much higher than 9v it'll probably go into thermal shutdown anyway.
You have three choices to get a higher current than 1A.
The
- LM78S05 delivers 2A,
- LM7805K delivers 3A (TO3 package)
- LM7805 delivers any current if you boost it with a power transistor. (The max. current splits into two currents where the LM7805 will stay at 800mA if the dimensions are correct.)
i'm running a stepper motor with a supply from LM7805 , my problem is the stepper draws more than 1.3 A , so the regulator goes so hot in a few seconds ,
i need to use another regulator LM too , but can stand this high current ,
i know the 138, 338 ..... i don't like them they are variable , i need a constant one like the 7805 and high current
Perhaps you need a regulator that can deliver at least a peak of 2.5 times the measured load on stepper motor. Thus it is better to work with a regulator mod (with series pass element) to handle a peak load of 5AMPs to be consistently stable.please study the series pass elements to increase the current load to 5 amps. As mentioned by Bill , you definitely need a Good heat-sink for the entire power section.
Usually, the biggest contributor of heat to a linear regulator besides the current draw is the supply voltage. If you feed a 7805 from an 8v supply, you'll drop 3v across the part and at 1a of current, that's 3 watts of dissipation, easily handled. On the other hand, if you're supplying it from a 20v supply, that's a 17 volt drop across the regulator and at 1a, 17 watts of power dissipated.
Besides that, a 7805 usually reacts "negatively" to overcurrent spikes like that and tries to shut down unless you've hung a ridiculously-large amount of capacitance on its output.