GizmoWizard
Member
I’ve put together a prototype speedometer using a GPS module and PIC microcontroller. It would be used to replace the non-functional speedometer in my old car, for small vehicles that don’t already have one, etc. My prototype circuit works great but I’ve run into a problem in displaying the speed on a readout large enough to be seen from the driver’s vantage point. These are the only choices I know of:
LCD – This would be my first choice since my prototype is already driving a two-line character LCD, and it would use less parts and power. But I haven’t been able to find a character LCD with a large enough font size (character height).
LED – I’ve found a two-digit multiplexed LED module with 0.6” character height that would just barely be satisfactory. The PIC could directly run an LED display but couldn’t drive the 7-segment digits with enough current to be bright enough. Plus the continuous process would take up a lot of processing time away from the PIC’s other duties.
I could have the PIC drive two MC4511 BCD-to-7-segment latching chips but their outputs are not multiplexed, so that would require running 14 lines from the extra two ICs to two non-multiplexed digits; a significant pcb layout challenge.
Any other ideas? Can anyone help me with this please?
Gizmo
LCD – This would be my first choice since my prototype is already driving a two-line character LCD, and it would use less parts and power. But I haven’t been able to find a character LCD with a large enough font size (character height).
LED – I’ve found a two-digit multiplexed LED module with 0.6” character height that would just barely be satisfactory. The PIC could directly run an LED display but couldn’t drive the 7-segment digits with enough current to be bright enough. Plus the continuous process would take up a lot of processing time away from the PIC’s other duties.
I could have the PIC drive two MC4511 BCD-to-7-segment latching chips but their outputs are not multiplexed, so that would require running 14 lines from the extra two ICs to two non-multiplexed digits; a significant pcb layout challenge.
Any other ideas? Can anyone help me with this please?
Gizmo