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CT255 

 20  

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16.  Install C2, 10 uF electrolytic capacitor. Remember to observe polarity 
with electrolytic capacitors! Check the parts placement diagram for correct 
orientation. 

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17.  Install R34, 10K ohm (brown-black-orange). 

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18.  Install R30, 10K ohm (brown-black-orange). 

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19.  Install R4, 10K ohm (brown-black-orange). 

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20.  Install R2, 10K ohm (brown-black-orange). 

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21.  Install C1, 1 uF electrolytic capacitor. Remember to observe correct 
polarity! 

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22.  Install R1, 47K ohm (yellow-violet-orange). 

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23.  Install R15, 100K ohm (brown-black-yellow). 

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24.  Install C6, .1 µF disc capacitor (marked 104 or .1). Disc capacitors are 
not polarized, so either direction is fine. 

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25. Install R39, 1K ohm (brown-black-red). 

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26.  Install R37, a precision 1K ohm (brown-black-black-brown-brown). 

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27. Install headers H2 and H1 by slipping the protruding pins on the short 
side through the circuit board and soldering. Solder all three pins. 

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28.  Install C3, .1 µF disc capacitor (marked 104 or .1). 

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29.  Install R31, a precision 4.22K ohm (yellow-red-red-brown-brown). 

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30.  Install R27, a precision 1.43K ohm (brown-yellow-orange-brown-
brown). 

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31. Install R40, the last 10K ohm (brown-black orange). 

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32. Install R23, a precision 1.82K ohm (brown-gray-red-brown-brown-
brown). 

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33.  Install R22, a precision 10K ohm (brown-black-black-red). 

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34. Install C5, .1 µF disc capacitor (marked 104 or .1). 

Whew! That was some work. But we’re almost done and some decisions need 
to be made before continuing. It’s a good time now to re-check all your work 
up to this point. Carefully inspect the circuit board for stray leads or open 
solder connections, trim and touch up any that need work. 

Next, while we are at our best, we will install the LED segments for the 
display. (L)ight (E)mitting (D)iodes are just that, a diode junction that emits 
light of a particular wavelength when forward biased, so pay attention to the 
polarity of the diodes as shown in the parts placement diagram. Remember 
that this will be the most observed part of the entire kit, so take your time and 

Summary of Contents for COMPUTEMP CT255

Page 1: ...onment Visibly counts up to the current temperature in binary numbers Eye catching display great for home or office Super accurate readout of 1 degree Celsius no calibration required Precision sensor...

Page 2: ...to Unbalanced Audio Converter Kit LC1 Inductance Capacitance Meter RAMSEY AMATEUR RADIO KITS HR Series HF All Mode Receivers QRP Series HF CW Transmitters CW7 CW Keyer CPO3 Code Practice Oscillator QR...

Page 3: ...cription 5 Schematic Diagram 13 Parts Layout Diagram 14 Parts List 15 Assembly Instructions 17 Case Assembly 23 Troubleshooting Guide 25 Conclusion 26 Warranty 27 KIT ASSEMBLY AND INSTRUCTION MANUAL F...

Page 4: ...ginal 6 page manual showing the stylish kit case that John Ramsey had spent his hard earned money on the die for when he was fresh out of college We have come a long way since then At the time this ca...

Page 5: ...n understand binary How do we do this easily Hang on here we go The binary counter U2 A and U2 B form a cascading ripple counter which is simply designed to count pulses on the clock pin pin 1 and out...

Page 6: ...o make conversions ADCs use much more complicated methods now to increase conversion speed but that is beyond this manual Now you know that each count is equal to 12 16mV so if you have a count of 100...

Page 7: ...ssible in this case about 3 9V When the voltage at pin 5 is below the voltage at pin 6 the output goes as low as possible or zero volts It is called a comparator because it is in reality comparing two...

Page 8: ...level that the charge on C1 can never reach It is greater than 5 0V due to R15 limiting the voltage on C1 to 3 4V so the comparator function is disabled Restarting the conversion cycle Now our count...

Page 9: ...lerant resistor is then 1 82K Now we have to find out what it takes for 100 0 degrees Fahrenheit to have a proper count of 100 0 on the display For this we need a voltage of 12 16mV 100 2 or 2 432 vol...

Page 10: ...would only deal with integer binary math but we at Ramsey like to mix things up a bit and throw in fractional binary math so you learn something new It is the basis of how all math works on computers...

Page 11: ...alue with the decimal point in place is now called a fixed point number This means that the decimal point can never move even when we perform mathematical operations on it This number is now considere...

Page 12: ...eading causing the reading to be incorrect sometimes This capacitor fixed that Imagine sanding the top corners of all of your stairs in a new staircase to smooth the freshly sawed edges It looks simil...

Page 13: ...CT255 13 CT255 SCHEMATIC DIAGRAM...

Page 14: ...CT255 14 CT255 PARTS LAYOUT DIAGRAM...

Page 15: ...ms brown black green R24 Precision Resistors with five color code bands or SMT 1 1K ohms brown black black brown R37 1 1 43K ohms brown yellow orange brown brown R27 1 1 82K ohms brown gray red brown...

Page 16: ...osophy This entails describing the circuit that you are building instead of just blindly installing components We hope that this will not only make assembly of our kits easier but help you to understa...

Page 17: ...ormance levels and it is extremely unlikely that any of your chips will have problems however we know that some of our hobbyists insist on socketing all IC components The addition of these will not vo...

Page 18: ...the hole in the part with the hole on the circuit board Use caution so as not to stress the leads when inserting or soldering Use the parts layout diagram as a guide for proper orientation Once you ha...

Page 19: ...g of it Believe it or not you are already halfway through the assembly of your kit Recheck your solder connections touch up any less than perfect connections that you see Watch out for any solder brid...

Page 20: ...stall C3 1 F disc capacitor marked 104 or 1 29 Install R31 a precision 4 22K ohm yellow red red brown brown 30 Install R27 a precision 1 43K ohm brown yellow orange brown brown 31 Install R40 the last...

Page 21: ...g assembly steps 37 Install C4 1 F disc capacitor marked 104 or 1 38 Identify and install remote sensor connector J1 towards the rear of the printed circuit board Gently slide the leads through the ci...

Page 22: ...uality shielded cable for remote sensing applications 41 Now that all of the parts have been installed configure the header jumper connections for either Celsius operation jumpers between pins one and...

Page 23: ...ng your kit In short TAKE YOUR TIME when assembling the enclosure This is the part that you and your friends will look at and admire for years 1 Lay the front and rear plastic plates over their corres...

Page 24: ...ensor is working correctly by pinching the temperature sensor U3 with your fingers and watching the temperature increase to about 98 de grees Remember that marvelous National Semiconductor IC give a p...

Page 25: ...e ac cess to an oscilloscope you can observe the oscillator section as well as the counter adding the bits STILL HAVING TROUBLE While we had hoped that it wouldn t come to this if you are still having...

Page 26: ...this Ramsey product As always we have tried to compose our manual in the easiest most user friendly format that is possible As our customers we value your opinions comments and additions that you woul...

Page 27: ...h be assured that the 1K ohm resistors are actually the missing 10 K parts Hum m m I guess the red band really does look orange Ramsey Electronics project kits are packed with pride in the USA If you...

Page 28: ...g Hands Holder for PC Board Parts HH3 Technician s Tool Kit TK405 Desoldering Braid RTS08 CT255 BINARY THERMOMETER KIT Quick Reference Page Guide Introduction 4 Circuit Description 5 Schematic Diagram...

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