On the bright side, here's a picture of the Calculator:
Monday, May 21, 2012
The Short, part 2
Today I tried powering the Calculator with my ATX power supply. I'm not sure the power supply still works.
On the bright side, here's a picture of the Calculator:
I am going to try booting a flashing LED code without the LCD. If it still shorts out, I know to just check the wiring. If it's the LCD, I'm not sure what I'll do.
On the bright side, here's a picture of the Calculator:
Sunday, May 20, 2012
The Short
There is a lurking short within the Calculator.
Since last post, I did very little up until today because I was quite busy. Today I finished up the hardware and software of the Calculator, and then tried to turn it on. Recall that last time, the regulator heated up and nothing happened. This time, the regulator heated up, nothing happened, and there was only 1.6 volts on the bus, not 3.3. I looked up the datasheet for the 7833 and realized that 4.5 volts was not enough to power it! I tried it with a 9v battery. Unfortunately, it didn't work. I then tried powering it off the VIn of an Arduino board. I accidentally plugged the 5v output into the Calculator, not the 3.3v output, and the LED backlight of the LCD came on. Nothing else happened. When I tried the 3.3v output, it only outputted 1.6 volts.
Next, I put a heatsink on the regulator, but it didn't work. Meanwhile, the resistance of the alleged "short" between ground and VCC ranged from 3k ohms to 7.5k ohms. I am thoroughly stumped. Tomorrow I will try powering the Calculator off of my ATX power supply. We shall see whether it requires more than 21 amps (!) tomorrow.
I plan to bring the unfinished Calculator in to school tomorrow.
Since last post, I did very little up until today because I was quite busy. Today I finished up the hardware and software of the Calculator, and then tried to turn it on. Recall that last time, the regulator heated up and nothing happened. This time, the regulator heated up, nothing happened, and there was only 1.6 volts on the bus, not 3.3. I looked up the datasheet for the 7833 and realized that 4.5 volts was not enough to power it! I tried it with a 9v battery. Unfortunately, it didn't work. I then tried powering it off the VIn of an Arduino board. I accidentally plugged the 5v output into the Calculator, not the 3.3v output, and the LED backlight of the LCD came on. Nothing else happened. When I tried the 3.3v output, it only outputted 1.6 volts.
Next, I put a heatsink on the regulator, but it didn't work. Meanwhile, the resistance of the alleged "short" between ground and VCC ranged from 3k ohms to 7.5k ohms. I am thoroughly stumped. Tomorrow I will try powering the Calculator off of my ATX power supply. We shall see whether it requires more than 21 amps (!) tomorrow.
I plan to bring the unfinished Calculator in to school tomorrow.
Monday, May 14, 2012
5 Volts and 4000 Ohms
It's been a while since my last post. Just FYI:
After furious work on Wednesday and Thursday, I had all of the hardware finished. I was about to test the calculator when I realized I didn't know what the LCD pinout was. And then it hit me. Here I was, with a 3 volt MCU, trying to hook up a 5-VOLT LCD! Anyways, I tested the LCD out, and it did not work at 3 volts. I ordered another, 3-volt lcd from Sparkfun late Thursday night, and it didn't come until today. With the LCD soldered now, I tried to test it out, but the backlight of the LCD would not turn on, and the voltage regulator grew hot. Although there are no obvious shorts, the resistance of Vcc to Ground is apparently 4000 ohms. Even that shouldn't have stressed out the regulator, though. Maybe I just inserted it backwards. I am done for tonight, though, and tomorrow being my 14th birthday, I doubt much work will happen until this Wednesday.
- The deadline has been extended to a shaky by next Monday.
- I am using a 16 by 2 character LCD instead of the 7-segment displays to keep the hardware simple.
- I had done pretty much no work on the calculator since Wednesday.
After furious work on Wednesday and Thursday, I had all of the hardware finished. I was about to test the calculator when I realized I didn't know what the LCD pinout was. And then it hit me. Here I was, with a 3 volt MCU, trying to hook up a 5-VOLT LCD! Anyways, I tested the LCD out, and it did not work at 3 volts. I ordered another, 3-volt lcd from Sparkfun late Thursday night, and it didn't come until today. With the LCD soldered now, I tried to test it out, but the backlight of the LCD would not turn on, and the voltage regulator grew hot. Although there are no obvious shorts, the resistance of Vcc to Ground is apparently 4000 ohms. Even that shouldn't have stressed out the regulator, though. Maybe I just inserted it backwards. I am done for tonight, though, and tomorrow being my 14th birthday, I doubt much work will happen until this Wednesday.
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