Products > Test Equipment
finding short on motherboards with a shorty (with display)
cybermaus:
Not sure I see the difference with your earlier rendering?
And both of these renderings are the same?
But while indeed I think the display is rather "north" and not very centered, I do not think it is very important either way.
As long as it works.
Also, if you want the display a little more centred on the box,you could place the 9V battery on the other side.
nikifena:
Nice project! Thanks for sharing.
Just a few ideas. What about adding an input protection circuit - two back-to-back 5V Zener diodes or unidirectional TVS?
In order to reduce the HF noise what about a 100pF capacitor across R7 and R8 and for better HF DC filtering 100nF across C3.
And more. Using off-the-shelf battery chargers with a USB port it could be done with a li-ion battery. Here is a good example: https://www.aliexpress.com/item/1005001466320793.html
nikifena:
Hi everyone again.
I was thinking about how to improve the project, so here are my ideas:
1. Switching to tactile switches for powering and all other functions. Using 12mm tactile switches with caps has a few benefits - they sit well next to the display and the height is good to fit everything into a box. Also, having an electronic power on, there could be integrated auto power off. Two switches can be used for four different things:
SW1 short press - on/off
SW1 long-press - mute
SW2 short press - relative mode
SW2 long-press - calibration
Auto power off after some time 30-60seconds when the tester is not used.
2. Adding a lithium battery with a built-in charger and battery protection - usually, there are cheap PCBs from Aliexpress and they could be used here in order to make the project simpler. I realized that there is not necessary to have a 5V boost circuit. The voltage from a single battery can be used directly to power the Arduino and the display board. Only the current source left, so I suggest using a precision reference voltage with an enable pin. I found LT4120 as a good solution. There is a version with 2.5V output. Just an extra transistor will increase the current capabilities. A precision voltage source will improve the stability and the readings too.
3. Adding relative mode. There are two ideas:
-A classic relative mode - Just connect the probes to the circuit and press the relative mode to zero the reading or
-First select relative mode, then connect the leads to the circuit. When the value reading is stable, a beep indicates that the relative mode is used. In this mode, when a low value is measured, two fast beeps could indicate that for faster short finding.
4. Increasing the range of the unit. This could be done for the next revision of the unit. Switching some resistors could do that. There could be two more ranges - micro ohm range and ohm range (up to 100 ohms for example) The ranges could be automatically selected.
I've been working as a PCB designer for the last few years, so I'm happy to do a good-looking PCB. I can't modify the code, so I will be happy if kripton2035 will agree to improve the whole project.
I will put a schematics idea soon.
kripton2035:
Everybody is free to do what they want with this project, that's why I published it.
so you can have a li-ion charger if you want. I prefer a simple 9v liion battery because I have plenty of them.
I HATE auto power off systems because they NEVER really switch off. and when you need the device that sat in a drawers for some time, the battery is flat
this never happens with a good old mechanical switch.
I'm already thinking at REL mode and greater range, but as you said it will be for the next release.
kripton2035:
anyway your idea of moving the din plug and the arduino to the bottom to have room for the display and button is very nice. adopted !
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