One of them is my multimeter UT61E from UNI-T that is a pretty good multimeter for the hobbyist.
The onboard processing chip ES51922 have more features than is presented to the user. This hack enables some of them.
After the modification my multimeter have the following additional features;
- Backlit LCD with backlight auto shut-off
- DMM auto power-off after 15 minutes
- Possible to Enable/Disable RS232. Default is to have RS232 Disabled
- MAX-MIN mode for Frequency and Duty cycle measurements
- AC Low Pass Filter mode
There are some more tweaks to the tweak that can be done;
- Increase LCD backlight shut-off time from 60 to 180 seconds by connecting BKSEL (113) to VB_ (-3V). It is floating by default
- Increase the auto power-off time to 30 minutes by connecting APOSEL (112) to VB_. Default is floating.
I add more modes that is triggered by long-pressing each button or by pressing both buttons simultaneously or by holding down the yellow button while powering on.
This is not my own hack but rather a compilation of already existing hacks with some additions.
I have however not seen anyone done this with a PIC from Microchip. Nor using the PIC to drive the LEDs to protect the MM processing chip.
I have also enabled the LPF in AC-mode which I have not seen been done earlier.
Prerequisites
- 2 pcs LED. The forward current must not exceed 3V
- 1 pcs Resistor to limit the current to the LEDs. Its value depends on the LEDs forward voltage drop
- 2 pcs Resistor as a voltage divider for the BKOUT signal. Around 40k-60k should be OK.
- 1 pcs PIC16F688 microprocessor from Microchip
- 1 pcs 0.1uF capacitor for decoupling the PIC16F688
- Thin connection wire
- Hot glue and super glue is good to have
- PicKit2 or PicKit3 to program the PIC16F688 microprocessor
The modification
Download the source code from here,https://bitbucket.org/foogadgets/ut61e-modification
Build the hex-file.
Flash the PIC16F688 with the generated hex-file.
Solder the decoupling capacitor between pin (1) and (14) on the PIC.
Solder thin cables on all pins except pin (4).
Here is a video of the final result,
https://www.youtube.com/watch?v=KLrDdRcWR2Y
Some pictures;
Hi!I dont understand what pins (numbers)are B and D ?
ReplyDeleteThe idea is to cut the pcb leads from the blue and yellow button and input those signals to the PIC. Then I connect the PIC to the other side of the cut pcb leads so that the PIC is placed in between the buttons and the DMM microprocessor. You choose where it is best to cut the pcb leads from the yellow and blue button. You can see in the pictures where I have made the cut.
ReplyDeleteHi,
ReplyDeleteYou make me try PIC. Thank you for that.
I cannot understand one line in your code.
PORTA = (1<<DCAC | 1<<VHZ | 1<< LPF);
What does 1<<LPF here? LPF is output.
Can you please explain?
Congratulations for the tutorial! I´d like to make some remarks to save other people´s time:
ReplyDelete1) don´t forget to cut the tracks that connect pins 111 and 117 to -3V. I didn´t pay attention to that and spent a lot of time to find the reason why the RS232 and the APOSEL (low pass AC filter) didn´t work;
2) I sugest you use transformer´s wire (varnished copper wire) instead of plastic insulated ones, they pass easily through the PCB holes;
3) After everything work, use a electric motor varnish to stick the wires to the board so that they don´t move around or create tensions on the ICs pins;
4) the letters A,B,C,D can also be seen/understood in the page the autor refers in his tutorial: http://www.mjlorton.com/forum/index.php?PHPSESSID=q7nqfboqosqshnukt4gnrg7q01&action=dlattach;topic=284.0;attach=1814;image);
5) in the pictures I managed to see that the author used 56KOhm value to R2 and R3. I used too and it works fine;
6) I tried to use super glue to stick the SMD leds in the aluminum foil paper of the light guide but it didn´t work. I had to use hot glue for that;
7) white leds (6500K color) also work well and gives a great look to the display´s backlight;
Another thing I´ve noticed, aparently the LPF is not funcional, in the ES51922 datasheet is said that when the LPF mode is activated the AC indication blinks. Somehow when the max/min option was activated the key button (blue one) cannot be used to this function:
ReplyDelete1.1.5 Low-pass filter feature
ES51922 provides a 3-order low-pass filter to reduce the influence of high frequency noise above 1KHz(3dB). This LPF feature is available in all ACV or clamp_meter ACA modes. Set FC5 to low in these mode, the KEY bottom is use to activate the LPF feature. Press KEY bottom for less than 1 second force meter enter LPF mode, and the AC sign on LCD panel will blink until the LPF mode is canceled. When LPF is activated, most of noise above 1KHz will decay greatly. So we can obtain more stable and accurate readings on low frequency response.
Hi, for AC Low Pass Filter Mode It is necessary for the setting to be made at power on? I was thinking to do it with Double Long Press Button (I intend to do this with Attiny44). Thank you
ReplyDelete