uping power supply current

MrDEB · Sep 3, 2009

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??

Nigel Goodwin · Sep 3, 2009

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 · Sep 3, 2009

I found a solution

High Current Voltage Regulation - Electric Circuit
note that the present supply is a duel (9+, 0, 9-) but the display is omly needing 9v +.

Nigel Goodwin · Sep 3, 2009

MrDEB said:
High Current Voltage Regulation - Electric Circuit
note that the present supply is a duel (9+, 0, 9-) but the display is omly needing 9v +.

Like I said

MrDEB · Sep 3, 2009

I missed your first post

but you needed checking up on anyway ---lol

kchriste · Sep 3, 2009

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

MrDEB · Sep 4, 2009

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
tired already!!

blueroomelectronics · Sep 4, 2009

The Mondo Superprobe is a fun project, I've not built it myself but I think 3VO has.

PS if you're still looking for a 18F book (no BASIC though) this is a terrific book on C & asm.
**broken link removed**

MrDEB · Sep 4, 2009

Thanks, will look over link

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 · Sep 4, 2009

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

blueroomelectronics · Sep 4, 2009

PS if you haven't already install the Microsoft Consolas font
https://www.microsoft.com/DOWNLOADS...E4-7E40-4807-8A86-B3D36FAB68D3&displaylang=en

Then from MPLAB
Edit/Properties/Text/Select Font
Select the Consolas font @ about 12 size

The danish zero makes it easier to tell number 0 from letter O.

bountyhunter · Sep 4, 2009

MrDEB said:
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 · Sep 4, 2009

Never looked for a 3 amp regulator

Willlook at price and availibility.

bountyhunter · Sep 4, 2009

MrDEB said:
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.

MrDEB · Sep 4, 2009

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
as per link I posted.
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 · Sep 4, 2009

MrDEB said:
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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