I've taken a stab at getting some insight in the electronics stack exchange, and that led me to eventually order some fresh CD4050 chips, thinking that the batch I ordered off eBay were either broken or mislabeled. Here's the original post: http://electronics.stackexchange.com/questions/141830/cd4050-voltage-leaks-what-can-i-be-doing-wrong
The new batch behaves identically. So now I'm thinking that surely I must be in the wrong here. These are CMOS 4050's, specifically one batch of CD4050B and another of CD4050BE.
I want to use them to control a Nokia 5110 LCD (the PCD8544 controller). This controller is 3.3V logic, and I'm using a good ol' Arduino Uno, so a 5->3.3V logic level converter is necessary. Adafruit's tutorial recommends using a CD4050 hex buffer. I read the datasheet, which explicitly advertises it as a logic level converter (from high-to-low only of course).
The tutorial worked fine for me, but the screen was really faint, like it wasn't getting enough power. I plugged the voltmeter into my 3.3V rail... and it read 4.2V! :-/
This lead me on a circuitous journey that I won't share here, suffice to say I ended up with a really simple circuit, meant to test the CD4050.
1. LM7805 V-regulator (powered via 5V wall-wart) into one side of the breadboard (my 5V rail), and from there into Vin on the Arduino. (I also experimented with disconnecting the V-reg and powering via USB)
2. 3.3V from the Arduino board into the other rail, so I've got 5V on one side of the breadboard, 3.3V on the other.
3. Power the CD4050 from 3.3V
4. Plugin the Voltmeter into ground and the Vcc of the chip. Reads 3.3V (looking at it now: 3.28V)
5. Insert a resistor from output 1 (pin 2) into ground, and input into the 5V rail. All other inputs and outputs are grounded.
6. Voltmeter reads 4.2V. This is the WTF!? moment.
7. Disconnect power - voltmeter still reads 4.2V. More cursing ensues.
It's these moments when I really wish I had a mentor. Anyone know of a good electronics club in Denver, CO? Thanks for any help, and ask away! Tonight I'm going to be experimenting again with this.
Should I order a 74HC4050? I see those mentioned a lot, but I don't see any reason why these 4050s I have already should be misbehaving, unless all 22 of them are junk (first order had 10, second order had 12).
The new batch behaves identically. So now I'm thinking that surely I must be in the wrong here. These are CMOS 4050's, specifically one batch of CD4050B and another of CD4050BE.
I want to use them to control a Nokia 5110 LCD (the PCD8544 controller). This controller is 3.3V logic, and I'm using a good ol' Arduino Uno, so a 5->3.3V logic level converter is necessary. Adafruit's tutorial recommends using a CD4050 hex buffer. I read the datasheet, which explicitly advertises it as a logic level converter (from high-to-low only of course).
The tutorial worked fine for me, but the screen was really faint, like it wasn't getting enough power. I plugged the voltmeter into my 3.3V rail... and it read 4.2V! :-/
This lead me on a circuitous journey that I won't share here, suffice to say I ended up with a really simple circuit, meant to test the CD4050.
1. LM7805 V-regulator (powered via 5V wall-wart) into one side of the breadboard (my 5V rail), and from there into Vin on the Arduino. (I also experimented with disconnecting the V-reg and powering via USB)
2. 3.3V from the Arduino board into the other rail, so I've got 5V on one side of the breadboard, 3.3V on the other.
3. Power the CD4050 from 3.3V
4. Plugin the Voltmeter into ground and the Vcc of the chip. Reads 3.3V (looking at it now: 3.28V)
5. Insert a resistor from output 1 (pin 2) into ground, and input into the 5V rail. All other inputs and outputs are grounded.
6. Voltmeter reads 4.2V. This is the WTF!? moment.
7. Disconnect power - voltmeter still reads 4.2V. More cursing ensues.
It's these moments when I really wish I had a mentor. Anyone know of a good electronics club in Denver, CO? Thanks for any help, and ask away! Tonight I'm going to be experimenting again with this.
Should I order a 74HC4050? I see those mentioned a lot, but I don't see any reason why these 4050s I have already should be misbehaving, unless all 22 of them are junk (first order had 10, second order had 12).