• We recently switched our forum platform. If you experience any issues please email support@crystalfontz.com

CFAG160160B voltage concerns

Chief316

New member
I have the CFAG160160B hooked up to a microchip 18f452 microcontroller, using a 5V voltage regulator from a 15V source. I have pins 1 and 2 of the LCD connected to ground, 3 to 5V and 4 connected to Vdd and Vee with a 20K potentiometer. I was wondering if Vo, when measured directly without being connected to the circuit recommended in the datasheet should be around 4.7V. I'm having difficulties with the pin, since it wants to stay around 4.7 and does not go down past 0V. My voltage regulator, when the potentiometer circuit is connected always heats up almost instantly as if there is a great deal of current running through it.

So as to my original question, is the Vo pin supposed to be sitting at 4.7V when not connected?
Looking for additional LCD resources? Check out our LCD blog for the latest developments in LCD technology.
 

CF Tech

Administrator
Vlcd is listed at 17.4v, so for Vdd=5v, Vo should be (5v - 17.4v) = -12.4v.

It should not take much current to set Vo to -12.5v, a few mA at most.

Vo could certainly "float" to +4.7 -- I have never tried to measure that.

Are you sure that Vo is connected to the center pin of the pot? If it was connected to one of the ends, that would explain a lot.
 

Chief316

New member
the pot is placed correctly, and I tested it with a 5V and -15V at each end. We tried a voltage divider but it would not display anything on the LCD. When using the pot, Vdd varies from approx. 4.3 to 4.7V, Vo varies from 4V to 1V, and Vee goes from 1V to -16V. The voltage regulator quickly heats up, and if left on for over 20s begins to emit a burning scent. When not connected the voltages remain at Vdd=5v, Vee=-16V, Vo-=4.7v.

Using a multimeter we found that there was a 14 ohm resistance between pins 3 and 4. Our wiring is clean, but we do not know why when the three are connected to the pot (Vo always at the middle pin) the voltage regulator heats up instantly.
 

Tot

New member
I have had a VERY similar problem (see my other mails). CF Tech, please could you forward me any replies you have sent 'in the support ticket'?

Regards,

Tot
 
Top