# uping power supply current

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#### MrDEB

##### Well-Known Member
can a person build a power supply with several 78xx in parelle with each other to increase current?
one 78xx is only good for 1 amp w/ heat sink but if I put 3 78xx in parelle then we have 3 amp capacity??
reason is I have a spectrum analizer schematic that I was/ am playing with using 10 - lm3916 chips. 10 leds per chip and a 2watt 15 ohm resistor connected to 9v+ and all the leds. the 3916's are sinkimg current.
I recall audioguru helped with design but the question was raised about power supply for all the LEDs??
I would post schematic but presently on different computer and can't get hoversnap to post attachement??

#### Nigel Goodwin

##### Super Moderator
No, you can't just parallel 78xx's - but you can add a transistor to increase it's current, details are in the datasheet.

#### MrDEB

##### Well-Known Member

but you needed checking up on anyway ---lol

#### kchriste

##### New Member
Forum Supporter
Another method would be to split the LEDs into sections consuming less than 1A and power each section with it's own 78xx.

#### MrDEB

##### Well-Known Member
Thats a viable solution

when I get back to Idaho, will look at possiablities.
Was surfing the web and found on the mondo-technology site a super probe that has a frequency countey on it. Wonder if I could use this to adjust all my displays and each filter section??
When I get back on my computer I have lots of stuff on my plate.
a digital Theremin using ADC and a MCP41010 digital pot
ordering PICs for experemintation with the two books I ordered on PICs
Doing same following PCBHEAVEN examples
Getting the bugs out of my critter ridder
getting it ready for a vechile ap

#### MrDEB

##### Well-Known Member

I purchased PICBASIC PROJECTS by Ibrahim Dogan
and
PIC in PRACTICE by D. W. Smith
also took great interest in the website suggested by ??
PCB Heaven I think
got to start somewhere and the projects for the 18F over at mondo-technology are really interesting.
can't waiot to get little juney out and get her a workout.
I purchased 5 18F1320's from Allied Electronics for under $3 each maybe learn something about converting from 16F to 18F wouldn't hurt Yo blueroom, I am still thinking about your manual on the junebug great tool that deserves a complete manual. Like adapter boards, better explanation about dip switches, etc. something catered to a newbi #### blueroomelectronics ##### Well-Known Member I agree about the manual, let alone a complete book. I've been playing with priority interrupts and wrote the following little demo. (Even with code tags it's sloppy thanks to the MPLAB editor) Button #1, LED #1 are high priority Button #2, LED #3 are low priority You can press #2 , #1 But can't press #1, #2 Turn off DIP 1 so the reset switch works after programming. Code:  list p=18F1320 include <p18F1320.inc> CONFIG OSC = INTIO2, WDT = OFF, LVP = OFF org 0x000 ; reset vector bra Init ; goto initialize org 0x008 ; high priority interrupt vector bra HiInt ; goto high priority interrupt org 0x018 ; low priority interrupt vector LowInt bcf TRISA,6 ; Light LED 3 bcf TRISA,7 bsf TRISA,0 bsf LATA,6 bcf LATA,7 bcf INTCON3,INT2IF ; clear the INT2 interrupt flag Loop1 bra Loop1 ; endless loop retfie HiInt bcf TRISA,0 ; Light LED 1 bcf TRISA,6 bsf TRISA,7 bsf LATA,0 bcf LATA,6 bcf INTCON,INT0IF ; clear the INT0 interrupt flag Loop2 bra Loop2 ; endless loop retfie Init clrf INTCON2 ; enable PORTB pullups, falling edge interrupts setf ADCON1 ; make all I/O digital setf TRISA ; turn off all the LEDs bsf INTCON,INT0IE ; enable INT0 (RB0) ; RB0 is always high priority bcf INTCON3,INT2IP ; INT2 (RB2) low priority bsf INTCON3,INT2IE ; INT2 interrupt enable bsf RCON,IPEN ; interrupt priority enable bsf INTCON,GIEL ; low priority interrupt enable bsf INTCON,GIEH ; high priority interrupt enable Loop3 bra Loop3 ; endless loop END #### bountyhunter ##### Well-Known Member can a person build a power supply with several 78xx in parelle with each other to increase current? one 78xx is only good for 1 amp w/ heat sink but if I put 3 78xx in parelle then we have 3 amp capacity?? of coarse add several capacitors reason is I have a spectrum analizer schematic that I was/ am playing with using 10 - lm3916 chips. 10 leds per chip and a 2watt 15 ohm resistor connected to 9v+ and all the leds. the 3916's are sinkimg current. I recall audioguru helped with design but the question was raised about power supply for all the LEDs?? I would post schematic but presently on different computer and can't get hoversnap to post attachement?? maybe just wait until I return to Idaho?? Why not make your life simple and just buy a 3A regulator? There are lots to choose from. #### MrDEB ##### Well-Known Member Never looked for a 3 amp regulator Willlook at price and availibility. #### bountyhunter ##### Well-Known Member Willlook at price and availibility. Linear Technology's LT1085 is a very good one. Other companies also make the 1085, it's an industry standard part. Last edited: #### MrDEB ##### Well-Known Member 3A=yes 9V=no looked at Mouser and no go on 9v regulator at 3amps using a 7809, and 2 mje3055, aswell as several 1 ohm resistors for under$4
a LM323T = \$1.27 but not 9v?? need to recheck my figures and data sheets.
As stated I have 10 LM3916's with 10 LEDs per. the LM3916's are sinking.
In my schematic I have 1=15 ohm resistor connected as 9+v to the LEDs.
why I came up with this configuration?? Audioguru was helping design and as per his suggestion (pretty sure it was audioguru, if not I apologize)
would love to post schematic but not on my computer.
The multiple 7809s sounds viable as well, then I don't need the 1 ohm resistors but will have to redesign the boards with several 7809s incorporated or ??

#### bountyhunter

##### Well-Known Member
The multiple 7809s sounds viable as well, then I don't need the 1 ohm resistors but will have to redesign the boards with several 7809s incorporated or ??
That's the best solution because it spreads the power out. be sure to make a PC area to lay the 78 over and solder down as a heatsink. One square inch of copper should be enough.

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