Hi,
I am trying to build a frequency counter following the instructions at Frequency counter with PIC and 4- to 5-digit LED display. I am using Variant 2, with a PIC16F628A. My 7-segment common anode display only has 4 digits, so I remove the part to control the 5th digit (including R10, D1, D2, D3, D4 and transistor T1) from the diagram.
I build it on a veroboard. Unfortunately, it does not work properly. Upon power on, the display shows a single digit "8." for 1 second (to indicate initialization), followed by "***0" where * represents the top half of a "0". See the following photos. I notice the top half of the display is slightly brighter than the bottom half.
**broken link removed**
**broken link removed**
The display seems to be counting the input frequency properly, although some segments cannot be displayed.
Upon investigating the PIC output with an oscilloscope, I notice something really strange:
+ Output of pin RA1 to control digit #4 is either 0 or 5V with no display connected, but drops to either 0 or 2.5V with the display connected.
+ Output of pin RB5 to control segment G is correct when the display is not connected, but always stay at 5V with the display connected.
I have checked all connections and despite the messy wiring, there seems to be no problems. Yet I could not get it working. Could it be because I am using the "A" version of the PIC, or perhaps because the PIC does not provide enough current to drive the display?
Any advice is appreciated. Have been spending my whole Sunday on this.
Thanks.
I am trying to build a frequency counter following the instructions at Frequency counter with PIC and 4- to 5-digit LED display. I am using Variant 2, with a PIC16F628A. My 7-segment common anode display only has 4 digits, so I remove the part to control the 5th digit (including R10, D1, D2, D3, D4 and transistor T1) from the diagram.
I build it on a veroboard. Unfortunately, it does not work properly. Upon power on, the display shows a single digit "8." for 1 second (to indicate initialization), followed by "***0" where * represents the top half of a "0". See the following photos. I notice the top half of the display is slightly brighter than the bottom half.
**broken link removed**
**broken link removed**
The display seems to be counting the input frequency properly, although some segments cannot be displayed.
Upon investigating the PIC output with an oscilloscope, I notice something really strange:
+ Output of pin RA1 to control digit #4 is either 0 or 5V with no display connected, but drops to either 0 or 2.5V with the display connected.
+ Output of pin RB5 to control segment G is correct when the display is not connected, but always stay at 5V with the display connected.
I have checked all connections and despite the messy wiring, there seems to be no problems. Yet I could not get it working. Could it be because I am using the "A" version of the PIC, or perhaps because the PIC does not provide enough current to drive the display?
Any advice is appreciated. Have been spending my whole Sunday on this.
Thanks.
Last edited: