Battery replacement for battery-only Igaging DROs?

AGCB97 said:
Were the PCBs you used 'off the shelf' or special made? If special, from where?
Thanks
Aaron
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I designed the PCB myself. I used EasyEDA, which is a web-hosted EDA system. It has plusses and minuses. On the plus side, it's free (with caveats), has a fairly large part library, and, since it's browser- based it can be used with just about any computer operating system. It's got an autorouter but I didn't like the result when I tried it. You get some choices w/regard to board color and thickness, which was useful when it came to adapting the cable-specific USB jack to my PCB. They have a "cutout" feature that also was quite handy in that regard.

Negatives are: the PCB manufacturer is in China so delivery times can be on the slow side; and the free version doesn't allow private designs (that's the caveat I mentioned), so any EasyEDA user can view your designs. That doesn't mean they could use your design -- if you don't include any comments it could be pretty difficult to figure out just what it's for! If you take this route make sure you have your own notes so YOU can figure it out :).

You can use your own PCB design S/W like Eagle, or KiCad to generate Gerbers that you can send to their PCB manufacturer. That way you can protect your IP a little more, but still get really inexpensive boards.
 
The high current consumption I observed appears to be related to the display. When I press the "off" button on the display box the current goes down to a few micro-amps. It doesn't totally power down because it maintains its position information as long as the batteries are good. Unfortunately, those scales don't have an auto-power-off feature, so to maximize battery life on this one it really is necessary to turn it off.

When I first measured the current draw, I now recall that I did it on some newer scales I'd gotten for my lathe. So it's possible that all my older scales (currently installed on my mini-mill) draw about 1.5mA. Time to do some more measurements....
 
Measurements have shown that all of my older-vintage igaging DROs draw about the same current, ~1.5mA. Kind of blows my simple RC filtering scheme out of the water, so I guess it's time to go back to the drawing board. I knew there likely was going to be a version 2 of the board anyway....
 
I like easyeda also, it's easy to pick up and has a good feature set. It has a couple glitches
-M
 
Here's a screen shot of my revised battery replacement board. It uses a 3.3V voltage regulator (on the back of the board) to handle the wide variation in supply current on my DROs. I added an LED + series resistor to front-light the DRO readout. Right now the DROs are not well illuminated so it makes it difficult to read them. $5 for ten boards (that's fifty cents apiece and includes silk screen on both sides, solder masks and through-hole plated vias!). As before, the shipping cost more than the boards....

igaging external power.png
 
martik777 said:
I will no longer buy any of those igaging DRO's, nothing but trouble.
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I hear you. I messed around with mine quite a bit before I fixed their noise-susceptibility problem.
 
RJSakowski said:
A different setup as I am using the iGaging scales with the Touch DRO. I had EMC problems with my lathe motor when the motor was switched off. I tried a number of solutions and finally end up soldering bypass capacitors across the power leads in the pickup heads. That solved my problem.
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RJ, what size was the cap and can you elaborate a little on exactly how/where it was installed? I have a similar problem described here:
www.hobby-machinist.com

IGaging DRO EMI Problem

I just finished a restoration of an old family lathe and added many upgrades. Among them was a three-phase motor with VFD and two iGaging Absolute DROs. The build thread is here. https://www.hobby-machinist.com/threads/new-caretaker-of-two-12-craftsman-lathes.87335/ I can be pretty handy with...
www.hobby-machinist.com www.hobby-machinist.com

Best,
Kelly
 
I put 1uF caps in my read heads and they helped a lot but did not completely solve my particular problem. Neither did some more extensive circuit board surgery where I inserted a resistor in the Vcc line to implement a filter. I had to cut a trace on the circuit board to do that, not something everyone wants to or is able to do.

I'm curious as to what RJ did, too.
 
Version 2 of my battery replacement design seems to work OK -- the DRO powered up and doesn't exhibit any problems w/regard to noise pickup. Here's a photo of the assembled board, including the mini-B USB receptacle and jack:
battery replacement.JPG

The diode is to prevent damage to the adapter and DROs if the external voltage source is accidentally connected backwards, and also prevents transients from discharging the 1uF capacitor on the input side of the regulator. While the latter might seem to be overkill, in fact I have observed DRO behavior that could only occur if the voltage to the sensor has been driven close to ground by external noise pulses.

Doing the same thing for newer DROs that use the micro-B connectors is a bit more challenging, at least as getting a board-mounted micro-B usb jack goes. I had to get creative with what I could get for mini-B jacks -- they seem to be designed to be used as part of a USB cable, not a PCB. In this case, I figured out that a couple of board cut-outs would allow me to install the metal shell so I can solder it to the board for mechanical strength. The shell MUST be used to fully implement the USB jack so it's not an option to just toss it.

As I mentioned in an earlier post, I also have included a resistor so I can illuminate the readout with an LED. The LED would be on the end of a pair of solid-core wires that can be bent to aim the light at the display.

One thing I noticed is that the weight of the USB cable hanging on the end of the board applies some force to the USB jack. I need to do some cable management to address this.
 
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