'Project:' Power Supply 15vdc @ 3 Amps

Thread Starter

kbyrne

Joined Dec 10, 2011
92
That is a duplicate schematic to mine By G. Randy Sloan. Alinear output can be obtained with a LM3914 inserted in place Of the LM3916. This circuit works on 15VDC & 12VDC due to ZD1, R3, & C2. For you needs See if you can find Texas Instruments Application Report SLOA058 - November 2000. A Single - Supply Op-Amp Circuit Collection. If you need I can upload it in Cute PDF format for you all to copy. Just say the word. Thankyou all for advise and input. Addition capacitors a go due to decoupeling needs.
 

t06afre

Joined May 11, 2009
5,934
If you need I can upload it in Cute PDF format for you all to copy. Just say the word. Thankyou all for advise and input. Addition capacitors a go due to decoupeling needs.
Yes please your pictures was to blurry to get the full picture. I think PDFs still are the best option.
 

Thread Starter

kbyrne

Joined Dec 10, 2011
92
Be looking in near future for Texas Instruments PDF. I have Foxit Reader and Cute PDF. Any reader should work A-OK.
 

Thread Starter

kbyrne

Joined Dec 10, 2011
92
I get very sharp schematic images from a PDF document by snagging the image out using "screenhunter" which is free snagit program that creates JPEG images from anything showing on the screen.
I use Jing freeware for the same reason. Go pro gets a person to Snagit & Jing.
 

Audioguru

Joined Dec 20, 2007
11,251
I cropped your fuzzy schematic to move its parts closer together, it could be much closer than mine. Then I zoomed in on it to be twice the original size. It would be much clearer if it was originally made with the parts closer together. Your schematic drawing software has fuzz-balls all over it.
 

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kbyrne

Joined Dec 10, 2011
92
On your gif the part in red is part # LM3914N. Schematic called for LM1458 Dual
Op-Amp And LM3916. Author said any garden varity Op-Amp will work so TL071 was chosen due to single OP-AMP and other legs not necessary. LM3914 is also used but results will vary between LM3916 & LM3914. Sinc current is 5.5MA
with resistor at end of line R8. Can be altered with R6 2.2kohm between legs 7 & 8 if need be. How will all of this affect overheating talked about. I am working on getting better quality gif's for future use. Thankyou for all the advise and feedback thou.
 

Audioguru

Joined Dec 20, 2007
11,251
You should use an LM3914 for a voltmeter and use an LM3915 for a VU meter.

The 2.2k resistor between pin 7 and pin 8 will have 1.28V across it then a graph in the datasheet shows that the LED currents will be only 5.5mA which is fairly dim.

I can't see the details in your fuzzy schematic so I don't know the supply voltage nor the LED voltage so I can't calculate the heating of the IC. It looks like a 68 ohm resistor is in series with the LEDs that shares the heat.

You can calculate the heat yourself. It is simply the voltage across the IC outputs multiplied by the total current. The 68 ohm resistor has the total LED current in it so it has a voltage drop that is subtracted from the IC output voltages.
 

t06afre

Joined May 11, 2009
5,934
An LM3914 is a voltmeter with linear steps. The lowest steps (100mV, 200mV, 300mV) are very far apart and the highest steps (800mV, 900mV, 1000mV) are very close together
An LM3016 was called a VU meter IC but maybe it is not made anymore. Its steps in the center are close together and the lowest steps are far apart.
The LM3916 used in the velleman kit, Is still in production http://www.national.com/mpf/LM/LM3916.html#Order Also the velleman kit k-4304 is rated for a voltage up to 15 volt. The 68ohm/1watt resistor may be to big in bar mode. I would have replaced it with a 56ohm same wattage resistor. Given that you use 20mA as LED current. Then all LEDs are on it will have power dissipation equal to 0.8 Watt approx.
 

Thread Starter

kbyrne

Joined Dec 10, 2011
92
Guys: I just uploaded a different png of the same schematic. See if it is easier to read and let me know so I will know for the future. I am experementing trying to get a good system. I have used LM3914"s before @ 12vdc but with a different schematic to success. Other schematic had a input delivered with a audio transformer and no OP-Amp. I will check out while I am building what you said and in the future post the results. Thankyou for the advise.
 

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