Anyone built the power supply from "electricity & electronics" by randy
slone?

I just completed construction of this power supply and made the
modifications on page 333 using the IC voltage regulators (nte956 and
nte957). My input voltage is about 36v however the output voltage from
the IC is about 28v.

The previous circuit that did not use the IC's gave a variable output
of about +- 3.8 to 36 volts DC. Now I'm getting about +- 1.2 to 28.
I'm wondering that if incorporating the IC's to improve the voltage
regulation under load is the cause of this? Is this the expected
outcome?

Here is a diagram of the positive side of the regulated power supply.


36V
raw
+dc__________________NTE956_______________________ ___________Regulated
V Pos.
| | | |
| | | |
+ |_____220 ohm 2W 10uF 35VDC
4700uF 50W | |
- 5Kohm 2W potentiometer 10uF 35VDC
| | |
| | |
Circuit Common Circuit Common Circuit Common

"Sparta" wrote in message
oups.com...
Anyone built the power supply from "electricity & electronics" by randy
slone?

I just completed construction of this power supply and made the
modifications on page 333 using the IC voltage regulators (nte956 and
nte957). My input voltage is about 36v however the output voltage from
the IC is about 28v.

The previous circuit that did not use the IC's gave a variable output
of about +- 3.8 to 36 volts DC. Now I'm getting about +- 1.2 to 28.
I'm wondering that if incorporating the IC's to improve the voltage
regulation under load is the cause of this? Is this the expected
outcome?

Here is a diagram of the positive side of the regulated power supply.


36V
raw
+dc__________________NTE956_______________________ ___________Regulated
V Pos.
| | | |
| | | |
+ |_____220 ohm 2W 10uF 35VDC
4700uF 50W | |
- 5Kohm 2W potentiometer 10uF 35VDC
| | |
| | |
Circuit Common Circuit Common Circuit Common


Your circuit can't possibly produce a +36 volt output due to a couple of
reasons.
(1) The NTE956, which is the equivalent to the standard LM317 voltage
regulator, needs a 3 volt minimum differential between input and output
voltages. Given your +36V input, the best that this regulator can produce
is +33 volts.
(2) Use the equation Vout = 1.25 (1 + (R2/R1)) + R2(Iq) to calculate the
resistor values. As you can see by the equation, your resistance values
will produce Vout of 29 volts... close to what you are getting. (R1 = 220
ohms and R2 is the 5K pot in your diagram).

In order to increase the Vout of your circuit, you'll have to either
increase the total resistance of the pot or decrease the resistance of R1.
Use the formula to calculate values to suit. Hint... it's a lot easier to
calculate for a smaller R1, because of the limited selection of values for
common pots.


--
Dave M
MasonDG44 at comcast dot net (Just subsitute the appropriate characters in
the address)

Never take a laxative and a sleeping pill at the same time!!

"Sparta" writes:

Anyone built the power supply from "electricity & electronics" by randy
slone?

I just completed construction of this power supply and made the
modifications on page 333 using the IC voltage regulators (nte956 and
nte957). My input voltage is about 36v however the output voltage from
the IC is about 28v.

The previous circuit that did not use the IC's gave a variable output
of about +- 3.8 to 36 volts DC. Now I'm getting about +- 1.2 to 28.
I'm wondering that if incorporating the IC's to improve the voltage
regulation under load is the cause of this? Is this the expected
outcome?

Here is a diagram of the positive side of the regulated power supply.


36V
raw
+dc__________________NTE956_______________________ ___________Regulated
V Pos.
| | | |
| | | |
+ |_____220 ohm 2W 10uF 35VDC
4700uF 50W | |
- 5Kohm 2W potentiometer 10uF 35VDC
| | |
| | |
Circuit Common Circuit Common Circuit Common

You can figure it out yourself. The voltage regulator's mission in life
is to make sure there is about 1.25 V across the 220 ohm resistor.
In order for that to be the case (assuming there is negligible
current from the IC common terminal), then you have a voltage divider
formed by the 220 ohm resistor and 5K pot. Comes out to a bit over 28 V.

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contact me via the Feedback Form in the FAQs.

Thank you both very much for your help! I am very new to this and was
just going back and reviewing the voltage gain equations for a non
inverting voltage amplifier and transistor amplifier circuits that
still have my head spinning. Thank you again as this certainly has
helped.

Tai West

Sparta wrote:
Anyone built the power supply from "electricity & electronics" by
randy
slone?

I just completed construction of this power supply and made the
modifications on page 333 using the IC voltage regulators (nte956 and
nte957). My input voltage is about 36v however the output voltage
from
the IC is about 28v.

The previous circuit that did not use the IC's gave a variable output
of about +- 3.8 to 36 volts DC. Now I'm getting about +- 1.2 to 28.
I'm wondering that if incorporating the IC's to improve the voltage
regulation under load is the cause of this? Is this the expected
outcome?

Here is a diagram of the positive side of the regulated power supply.


36V
raw

+dc__________________NTE956_______________________ ___________Regulated
V Pos.
| | | |
| | | |
+ |_____220 ohm 2W 10uF 35VDC
4700uF 50W | |
- 5Kohm 2W potentiometer 10uF 35VDC
| | |
| | |
Circuit Common Circuit Common Circuit Common