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.
(go directly to build notes)Temp Sense/Bias Ctrl Schematic
(Click for Full Schematic)
C:\Users\Rob\Documents\HamStuff\SDR\MOBO4_x\mobo43
(go directly to build notes)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)
| Check | Count | Component | Marking | Category |
|---|---|---|---|---|
| ❏ | 5 | 0.1 uF | SMT 0805 | |
| ❏ | 1 | 0.1 uF | SMT 0805 | |
| ❏ | 3 | 10 k ohm 5% | SMT 0805 1/8W | |
| ❏ | 2 | 2.2 k ohm 5% | SMT 0805 1/8W | |
| ❏ | 1 | 330 ohm 1% | SMT 1206 1/4W | |
| ❏ | 1 | LM317 SMT adjustable voltage regulator | LM317
 | SOT-223-4 |
| ❏ | 1 | AD5301 IC DAC 8BIT 2WIRE I2C SOT23-6 | AD5301
 | SOT-23-6 |
| ❏ | 1 | tmp101 IC Temp sensor | TMP101
| SOT-23-6 |
Temp Sense/Bias Ctrl Summary Build Notes
- Install Bottomside Ics
- Install Bottomside Rs and Cs
- Install Topside Ic
- Install Topside Rs and Cs
- Test the Stage
Temp Sense/Bias Ctrl Detailed Build Notes
Bottom of the Board
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.
| Check | Designation | Component | Marking | Category | Orientation | Notes |
|---|---|---|---|---|---|---|
| ❏ | U07 | tmp101 IC Temp sensor | TMP101
| SOT-23-6 | ||
| ❏ | U11 | AD5301 IC DAC 8BIT 2WIRE I2C SOT23-6 | AD5301
| SOT-23-6 | Take ESD precautions |
Install Bottomside Rs and Cs
| Check | Designation | Component | Marking | Category | Orientation | Notes |
|---|---|---|---|---|---|---|
| ❏ | C09 | 0.1 uF | SMT 0805 | Lyle, KK7P recommends deferring mounting C9 due to the nearby IC | ||
| ❏ | C16 | 0.1 uF | SMT 0805 | |||
| ❏ | C19 | 0.1 uF | SMT 0805 | |||
| ❏ | R18 | 10 k ohm 5% | SMT 0805 1/8W | |||
| ❏ | R55 | 330 ohm 1% | SMT 1206 1/4W | |||
| ❏ | R19 | 10 k ohm 5% | SMT 0805 1/8W | |||
| ❏ | R20 | 10 k ohm 5% | SMT 0805 1/8W |
Top of the Board
Install Topside Ic
| Check | Designation | Component | Marking | Category | Orientation | Notes |
|---|---|---|---|---|---|---|
| ❏ | U12 | LM317 SMT adjustable voltage regulator | LM317
| SOT-223-4 | Take ESD precautions |
Install Topside Rs and Cs
| Check | Designation | Component | Marking | Category | Orientation | Notes |
|---|---|---|---|---|---|---|
| ❏ | C14 | 0.1 uF | SMT 0805 | |||
| ❏ | C21 | 0.1 uF | SMT 0805 | |||
| ❏ | C50 | 0.1 uF | SMT 0805 | |||
| ❏ | R29 | 2.2 k ohm 5% | SMT 0805 1/8W | |||
| ❏ | R62 | 2.2 k ohm 5% | SMT 0805 1/8W |
Temp Sense/Bias Ctrl Completed Stage
Top of the Board
Bottom of the Board
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.
Test Measurements
| Testpoint | Units | Nominal Value | Author's | Yours |
|---|---|---|---|---|
| A (pin 2 or pin 4) to B (ground) | Ohm | 330 | TBD | _______ |
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
| Testpoint | Units | Nominal Value | Author's | Yours |
|---|---|---|---|---|
| U12 input voltage (pin 3) (K1-2 and K1-3 shunted) | V dc | 0 | tbd | _______ |
| U12 input voltage (pin 3) (K1-2 and K1-3 NOT shunted) | V dc | ~12 | tbd | _______ |
| U12 output voltage (pin 2) (U12-1 grounded) | V dc | 1.2 | tbd | _______ |
| U12 output voltage (pin 2) (U12-1 at +5V dc) | V dc | 6.2 | tbd | _______ |
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..