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problem to have 15v and 5v

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milanino

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this circuit give 15V output
what do I add to this circuit to have 5V?
I need to have 15v and 5v to power two different circuits
Help please
 

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The text on your schematic is impossible to read.
Please turn off the grid lines and the grey background.

The regulator has its pin 2 not connected to ground so its output might be 1V less than the unregulated voltage.
 

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It's 7805 regulator and 220v/18v transformator.
i forget to connect GND of the 7805 regulator.
i would like to have 15v to power LM1893 circuit and 5v to power pic18F
 
One simple idea would be to create the above circuit (corrected) twice.
One with a 7805 for 5V output and one with a 7815 for 15V output.
Depending on your current needs, you may even get away powering the 7805 from the 7815, for less thermal losses.

Take a look at TI's (www.ti.com) parametric search for LDOs you'll definitely find what you're looking for.
 
The 18V transformer produces a peak voltage of 25.5V when loaded and a higher voltage when not fully loaded. Why do you use a transformer with such a high voltage?
A 12V transformer produces 17V peak and the rectifiers reduce it to 15V. The 7805 regulator will be much cooler.
 
A 7815 regulator needs an input of at least 17.5VDC which cannot come from a transformer that is only 12V.
The LM1893 does not need a voltage regulator, the unregulated 15VDC from the 12V transformer and full-wave rectifier powers it perfectly.
The LM1893 is obsolete and is not made anymore.
 
One simple idea would be to create the above circuit (corrected) twice.
One with a 7805 for 5V output and one with a 7815 for 15V output.
Depending on your current needs, you may even get away powering the 7805 from the 7815, for less thermal losses.

.............................
Powering the 7805 from the 7815 will distribute the thermal loss of the 5V output between the two regulators but the total thermal loss will be the same, not less.
 
The transformer is a small high frequency signal transformer, not a low frequency power transformer (it does not have a full-wave bridge rectifier). The datasheet for the LM1893 talks about it.
The +18V is from an external power supply.
 
The LM1893 IC was used 18 years ago to send and receive slow data for a short distance over a power line.
It sent a carrier (50khz to 300kHz) modulated by frequency shift keying at two audio frequencies.
Its IC and its high frequency transformer are not made anymore.

Its datasheet tells you all about it.
 
The LM1893 was originally produced by National Semiconductor. National was bought by Texas Instrument a couple of years ago.

But, as has been mentioned at least 4 times in your various threads on this topic, it is obsolete. Why spend so much time designing around a component you may not be able to buy?
 
i have found LM1893 and it stays existing and products by Texas instrument
National Semi produced most LMxxxx ICs for many years.
A few years ago National was purchased by Texas Instruments.
Today on the website of Texas instruments they say the LM1893 is obsolete (not made anymore).
 
i have buy it
one problem i have with the pin 5 ??
how to have 1 logic for Tx and 0 logic for Rx. i link it with pic ??
 
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