What microcontroller is used in this LC meter?

The PIC16F628A microcontroller is used.

Can the device be battery powered?

Yes, it was made battery powered using a 3.6V Li-Ion 135 mAh battery.

How is 5V supplied for the LCD when using a 3.6V battery?

A TPS61222 boost converter is used to generate 5V from the 3.6V Li-Ion battery.

How is the Li-Ion battery charged?

Battery charging is handled by a MAX1811 Li-Ion charger IC and a USB connector was added for charging.

Were there major firmware changes to the original design?

No, only minor firmware changes were made; calculations remain as in the original firmware.

What firmware features were added or changed?

Changes include rearranged PORTB pinout for the LCD, the second LCD line showing oscillator frequency continuously, and automatic recalibration when switching between L and C modes.

Why was a small Li-Ion battery chosen instead of a 9V battery?

A 9V battery would not fit in the chosen project box, so a small 3.6V Li-Ion battery was used to make the device compact.

LC meter using PIC16F628A Microcontroller

I needed a good LC meter for my one of my next projects so I went and built the famous LC meter by Phil Rice.

By Ibrar Ayyub

PublishedJuly 21, 2022

Summary of LC meter using PIC16F628A Microcontroller

Summary: I built Phil Rice's LC meter, adding a compact battery-powered supply, USB charging, and minor firmware tweaks for improved display and auto-recalibration. The original measurement algorithm was kept intact while the device was made smaller and portable.

Parts used in the LC meter project:

PIC16F628A microcontroller
16x2 LCD display (compatible with 5V)
TPS61222 5V boost converter (Texas Instruments)
Inductor/coil for TPS61222
Decoupling and output capacitors for TPS61222
MAX1811 Li-Ion charger IC (Maxim)
3.6V Li-Ion battery (135 mAh, from Bluetooth headset)
USB connector for charging
Project enclosure/box
Miscellaneous passive components and PCB wiring

I needed a good LC meter for my one of my next projects so I went and built the famous LC meter by Phil Rice. This LC meter design is pretty old but since it is a perfectly good device there was no need to design/build/debug one of my own. So, I just changed the original firmware a bit and added few electronic goodies to it to make it more compact.

UPDATE: Project is on HackedGadgets, ...and now also on Hack-a-Day!

Power Supply
I wanted to fit it in this project box that I had laying around for some time and I also wanted it to be battery powered. There was no way that I could fit 9V battery in this project box along side with all the electronics, so I figured I could add a tiny 3.6V Li-Ion battery that I also had... laying around.

It is a 135mAh one from a broken Bluetooth headset. After having no luck in finding the appropriate 2x16 or 1x16 LCD that works at 3.6V I decided to incorporate a 5V voltage booster that will do the trick. For this purpose I selected TPS61222 power booster from Texas Instruments. This little (extremely little) device is very good and it requires just a coil and two capacitors to operate.

Now, because there is a Li-Ion battery in the device I needed a way to charge it properly. This is done by MAX1811 Li-Ion charger IC from Maxim. Later on, by placing a small USB connector on board, all power supply & charging problems were solved.

Firmware modifications
No critical firmware modifications were made. All calculations are performed as they were in the original firmware. Only a few small changes were made such as: PORTB pinout re-arranged for LCD display, second line of display constantly shows oscillator frequency, LC meter is automatically re-calibrated ("zeroed") when switching from L to C and the other way around.

For more detail: LC meter using PIC16F628A Microcontroller

What microcontroller is used in this LC meter?
The PIC16F628A microcontroller is used.
Can the device be battery powered?
Yes, it was made battery powered using a 3.6V Li-Ion 135 mAh battery.
How is 5V supplied for the LCD when using a 3.6V battery?
A TPS61222 boost converter is used to generate 5V from the 3.6V Li-Ion battery.
How is the Li-Ion battery charged?
Battery charging is handled by a MAX1811 Li-Ion charger IC and a USB connector was added for charging.
Were there major firmware changes to the original design?
No, only minor firmware changes were made; calculations remain as in the original firmware.
What firmware features were added or changed?
Changes include rearranged PORTB pinout for the LCD, the second LCD line showing oscillator frequency continuously, and automatic recalibration when switching between L and C modes.
Is the original LC measurement algorithm preserved?
Yes, all calculations are performed as they were in the original firmware.
Why was a small Li-Ion battery chosen instead of a 9V battery?
A 9V battery would not fit in the chosen project box, so a small 3.6V Li-Ion battery was used to make the device compact.

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Ibrar Ayyub

I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough...