Temp Sense/Bias Ctrl Introduction

General

This stage provides the onboard overtemperature protection in case the heatsink temperature exceeds a preset (default 55 deg C or 132 deg F, changeable by user) limit.

The builder installs the components necessary to implement the Temperature sensing and PA Bias control functionality.

It is always a good idea to double check the bill of materials in this set of documentation with the official BOM on the Mobo site. Discrepancies may be introduced inadvertently, as the changes are sometimes not communicated or discovered, making timely update of this site a problem.

Theory of Operation

The temperature sensor (TMP100) is placed close to the Final PA transistor and provides constant measurement of the temperature of that component. This is sent uip the I2C bus to the MPU which, in turn, monitors the temperature levels thuis measured. When the temperature exceeds programmed threshholds, the MPU sends a signal down the I2C bus to the AD5301 to output a contr5ol voltage into the LM317 voltage regulator, whose output is fed to the PA's bias circuitry, adjusting the bias until the measured temperatures are back in line with programmed expectations.

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Temp Sense/Bias Ctrl Schematic

(Click for Full Schematic)
Temp Sense/Bias Ctrlschematic

C:\Users\Rob\Documents\HamStuff\SDR\MOBO4_x\mobo43

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Temp Sense/Bias Ctrl Bill of Materials

Stage Bill of Materials

(resistor images and color codes courtesy of WIlfried, DL5SWB's R-Color Code program)

CheckCountComponentMarkingCategory
50.1 uFSMT 0805
10.1 uFSMT 0805
310 k ohm 5%SMT 0805 1/8W
22.2 k ohm 5%SMT 0805 1/8W
1330 ohm 1%SMT 1206 1/4W
1LM317 SMT adjustable voltage regulatorLM317 LM317SOT-223-4
1AD5301 IC DAC 8BIT 2WIRE I2C SOT23-6AD5301 AD5301SOT-23-6
1tmp101 IC Temp sensorTMP101 TMP101SOT-23-6

Temp Sense/Bias Ctrl Summary Build Notes

Temp Sense/Bias Ctrl Detailed Build Notes

Bottom of the Board

Temp Sense/Bias Ctrl Bottom View

Install Bottomside Ics

Use the MoboControl03 GUI to modify the I2C addresses, that in case ones kit comes with the TMP101 rather than the TMP100, then in the MoboControl GUI, in the "I2C Address Control" box, the address for "TMP100" should be changed from "78" to "74", followed by a push of the "Update" button.

Install Bottomside Ics photo
CheckDesignationComponentMarkingCategoryOrientationNotes
U07tmp101 IC Temp sensorTMP101 TMP101SOT-23-6
Take ESD precautions

>Kit may come with TMP101 rather than the TMP100

U11AD5301 IC DAC 8BIT 2WIRE I2C SOT23-6AD5301 AD5301SOT-23-6

Install Bottomside Rs and Cs

CheckDesignationComponentMarkingCategoryOrientationNotes
C090.1 uFSMT 0805
Lyle, KK7P recommends deferring mounting C9 due to the nearby IC
C160.1 uFSMT 0805
C190.1 uFSMT 0805
R1810 k ohm 5%SMT 0805 1/8W
R55330 ohm 1%SMT 1206 1/4W
R1910 k ohm 5%SMT 0805 1/8W
R2010 k ohm 5%SMT 0805 1/8W

Top of the Board

Temp Sense/Bias Ctrl Top View

Install Topside Ic

CheckDesignationComponentMarkingCategoryOrientationNotes
U12LM317 SMT adjustable voltage regulatorLM317 LM317SOT-223-4

Install Topside Rs and Cs

CheckDesignationComponentMarkingCategoryOrientationNotes
C140.1 uFSMT 0805
C210.1 uFSMT 0805
C500.1 uFSMT 0805
R292.2 k ohm 5%SMT 0805 1/8W
R622.2 k ohm 5%SMT 0805 1/8W

Temp Sense/Bias Ctrl Completed Stage

Top of the Board

View of Completed Top

Bottom of the Board

View of Completed Bottom

Temp Sense/Bias Ctrl Testing

Verify R55

Test Setup

Check R55, which is a 330 ohm resistor to ground.

Without power applied to the board, you can measure the resistance from the output of LM317 (pin 2 or the TAB, pin4) to ground - it should be 330 ohm.

Verify R55

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
A (pin 2 or pin 4) to B (ground)Ohm330TBD_______

LM317 Test

Test Setup

Perform this test with SR v6.3 connected and powered up

(1) Use a shunt to jumper pins 2 and 3 of K1 - this puts the Mobo in Rx mode.
(2) Measure LM317 input voltage (pin3) - should be zero.
(3) Remove the shunt from K1 - this will put the Mobo in Tx mode.
(4) Measure the LM317 input voltage (pin 3) - it should be S12V - or about +12V.
(5) Ground LM317 pin 1 and measure the output at pin2 - it should be +1.2V.
(6) Apply +5V to LM317 pin 1 and measure the output at pin 2 - it should be +6.2V.

When you have completed the tests, return the shunt to its normal position between pin 1 and 2 for normal operations.

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
U12 input voltage (pin 3) (K1-2 and K1-3 shunted)V dc0tbd_______
U12 input voltage (pin 3) (K1-2 and K1-3 NOT shunted)V dc~12tbd_______
U12 output voltage (pin 2) (U12-1 grounded)V dc1.2tbd_______
U12 output voltage (pin 2) (U12-1 at +5V dc)V dc6.2tbd_______

Test Program Requirements

Test Setup

  • Program should be able to read the output of the tempoerature sensor and display on the GUI screen the temperature, as it changes
  • Program should allow the user, using a slider or similar control, to increase and decrease the voltage at the output of the variable voltage regulator, while measuring the voltage at the output using a DMM
  • Program should permit the user to apply heat to the temperature sensor and display the sensor's temperature reading and also to programmatically control the voltage output of the variable voltage regulator in resoponse to the temperature change..