I want to design a circuit that will give me +5 and -5 volt of power. i got a schematic as shown here and assembled it.
**broken link removed**
I supplied 12V VAC to the circuit (i hope thats what should be supplied) However, when i power the circuit, the 7905 regulator heats up... it becomes very hot... there is no voltage in either +5 or -5.... the 7805 regulator is normal... whats wrong in this circuit? The 1000u cap are of 24V.
I want to design a circuit that will give me +5 and -5 volt of power. i got a schematic as shown here and assembled it.
**broken link removed**
I supplied 12V VAC to the circuit (i hope thats what should be supplied) However, when i power the circuit, the 7905 regulator heats up... it becomes very hot... there is no voltage in either +5 or -5.... the 7805 regulator is normal... whats wrong in this circuit? The 1000u cap are of 24V.
Check the pin-out wiring connections for the 7905, they are not the same as a 7805 and it's a rather common mistake to wire up a 79xx regulator as a 78xx regulator is wired. Find a data sheet for a 7905 and look carefully at the pin connections.
I think Lefty is correct. Notice that the pin sequence for 7805 is Input-GND-Output, but it's GND-Input-Output for 7905. try to exchange the connection of pin 1 and 2 of 7905.
More heat and power is wasted using 12v. 9 volts would be a better choice but 12v will work. Use adaquit (sp?) heat sinks and you're ok if thr transformer can supply the current.
Your half wave design will save some power.
hei i did the same ting to but im nt using transforme, but a pc power supply so i took a -12V supply as the input for the 7905 ic.... so i tink maybe ur supply of AC voltage gives the problem.... n i tell u wat its more easy and the voltage is more stable if u use the PC power supply...
As it's only halfwave rectified I would suggest keeping the current it supplies quite low, I'm dubious 2200uF would be enough for only halfwave rectification.
I would strongly advise getting a centre tapped transformer and using fullwave rectification.
2200:mu:F will be enough. With 12V in the ripple can be as high as 8V before the regulator will start dropping out. I simulated it on LTSpice and the minimum valley is 8.7V.