Question about Blu-DRO/Touch DRO

[vtcnc]

I did the DIY version and had to ground the system to a water pipe to get the interference to stop.

 

[BaronJ]

Hi Guys,

Easy ! Weight. Switching power bricks don't have a heavy transformer in them, linear ones do. If you get one each of similar ratings together you will see what I mean.

 

[Briney Eye]

I have read that switching to an older wall-wart transformer fixes most of these issues. I do have the problem with the tenths digit being slightly glitchy some of the time. The wall-wart is supposed to fix this. The power supply they include with the Bu-Dro kit is the problem. Yes, flourescent lights can effect the readouts and I am not trying to be rude but they are outdated and on their way out. LED’s are the way to go. Yes I understand it can be expensive to switch to LED’s and is not always practical but unfortunately the florescencent are part of the problem.
Try running the power supply from a different wall outlet or isolate it from any power source that is sharing power with a flourescent light. Lastly, sometimes the motor of these machines are not perfectly grounded any that can interfere with the scales. You can isolate the scale with a non conductive material. This helps tremendously. Oh and I also forgot, make sure the scale cables are not running or crossing a power supply or motor leads. This will effect them as well. I love my Blu-Dro and iGaging scales. They are very accurate and very very repeatable. I use them both on my mill which has a transplanted treadmill motor and my lathe with ony the occassional glitching problem on the mill, which honestly happens very little to the point that the wall-wart tranformer is not a must-do-now-mod. I also run all types of machinery in the background while the mill and lathe are running and they cause no interference

LED task lights can be the very worst offenders for generating noise, but it's luck-of-the-draw. I have a gooseneck LED that generates tremendous amounts of electrical noise, and one on an articulated arm that's perfectly quiet. I haven't noticed any issues so far with the LED replacements for incandescent bulbs.

The best solution to TouchDRO stability issues is installing decoupling capacitors in the scales themselves. After I did that to mine they were very stable (even with the gooseneck LED on). This shows the mod to a Shars scale (and yes, I should have trimmed the leads):

 

[JPigg55]

I've contacted Bill from iGaging in the past, he's of no help for technical support.
All he will do is tell you to send him your question via email and he'll forward it to his supplier.
Whether he forwards it or not, I'm not sure, but no answers will be forthcoming. They consider Yuriy and Touch DRO as competitors. I'm unsure why since they don't offer a true DRO, just displays for their scales.
One thing to check is if the USB cords are shielded. Some from iGaging are and some are not.
Here's a source for the obscure cable types iGaging uses: http://www.dcables.net/
It's difficult to find some of the cables like the male to male mini-B cords, but they do have them.

 

[9t8z28]

This is good to know. My Blu-Dro came with the cheap switching style. I’ve also heard that these switching types are not supposed to get hot but mine does. I looked and found 2 heavy power bricks in a box of old power supplies that no longer have a use. Good thing I hung onto these. I knew they would serve a purpose one day. One is 12V and the other is 6V. I am going to cut the cord off of each one and try both of them since I need two of them for the 2 Blu-Dro’s I have. Thanks BaronJ.

Hi Guys,

Easy ! Weight. Switching power bricks don't have a heavy transformer in them, linear ones do. If you get one each of similar ratings together you will see what I mean.

 

[9t8z28]

I have heard of this before but never really looked into it much. Where do you get these decoupling capacitors? How do I know which ones to get ? Thanks for posting this

LED task lights can be the very worst offenders for generating noise, but it's luck-of-the-draw. I have a gooseneck LED that generates tremendous amounts of electrical noise, and one on an articulated arm that's perfectly quiet. I haven't noticed any issues so far with the LED replacements for incandescent bulbs.

The best solution to TouchDRO stability issues is installing decoupling capacitors in the scales themselves. After I did that to mine they were very stable (even with the gooseneck LED on). This shows the mod to a Shars scale (and yes, I should have trimmed the leads):

View attachment 274509

 

[RJSakowski]

LED task lights can be the very worst offenders for generating noise, but it's luck-of-the-draw. I have a gooseneck LED that generates tremendous amounts of electrical noise, and one on an articulated arm that's perfectly quiet. I haven't noticed any issues so far with the LED replacements for incandescent bulbs.

The best solution to TouchDRO stability issues is installing decoupling capacitors in the scales themselves. After I did that to mine they were very stable (even with the gooseneck LED on). This shows the mod to a Shars scale (and yes, I should have trimmed the leads):

View attachment 274509

After reading your modification, I decided to modify mine. I used a .05 mfd disk and a 4 mfd electrolytic in parallel. The reasoning is that the disk capacitor has a better high frequency response and the electrolytic is capable of dealing with any longer duration voltage shifts. Rather than soldering to the ground plane as you have done, I decided to use the soldered mounting for the USB jack directly above the capacitor in your photo.

I had no inteference from fluorescent lighting or external voltage spikes. ?My readings would jump when I shut the lathe motor off. Moving the Arduino power supply yto a different outlet would diminish the frequency of the glitches and running on battery power would eliminate them but it was bither to be using a battery for power.

I will be watching to see if I have any further glitches.

 

[BaronJ]

Hi Guys,

Just about any 1000pf to 5000pf ceramic capacitor will do for that purpose. If you are going to use any on high voltage equipment, motor commutators, relay contacts, make sure that you use 500 volt or greater rating.

My mill motor, which uses brushes, now has a pair wired across the commutator. This completely kills the noise that used to come from it. I also fitted a mains suppression filter inside the control box. That one I salvaged from a dead computer PSU.

Fortunately non of the fluorescent lighting in the shop produce any interference. I've got a mixture of normal and electronic ballasted ones.

 

[homebrewed]

I have 3 of the older igaging scales on my mini mill. I've gone around and around with the noise issue. Here are things I've found to be helpful:

1. Shielding the cables. The cables that came with my scales were not shielded. I bought some copper braid and put it over the cables, then soldered wires from the shield to the DRO ground (I had to get inside the DRO remote receiver units to do it). Yuriy's Toys has a lot on this issue, as well.
2. Bypass capacitors across the read head's internal power supply connections. I used 1uf plastics to good effect. On mine, Vcc and Gnd were clearly marked on the PCB so it was easy to do.
3. Do not use the provided mounting hardware, unless you insulate the scale from the hardware using electrical tape. I made my own mounts out of Acetal.

If the readings start to jump around after awhile, that usually is an indication that the batteries are getting low. Low supply voltage increases the unit's noise susceptibility.

I bought a wall-wart from Jameco that has a 9VAC output, so I know it has an old style 60Hz transformer in it, so no noise from a switcher; and good isolation from the power line. I've got diode bridges, capacitors and voltage regulators left over from my days as an electronics engineer (plus some perf board) so I'm going to make a power supply to get rid of the batteries. Hopefully the extra wires don't act as antennae (but I do have more shielding braid if needed).

For those who don't want to make this kind of power supply, FYI two series-connected D cells would outlast the CR2032's in the DROs by a substantial amount. Places like Jameco sell battery holders for a wide variety of battery configurations.

 

[Briney Eye]

I have heard of this before but never really looked into it much. Where do you get these decoupling capacitors? How do I know which ones to get ? Thanks for posting this

Hi Guys,

Just about any 1000pf to 5000pf ceramic capacitor will do for that purpose. If you are going to use any on high voltage equipment, motor commutators, relay contacts, make sure that you use 500 volt or greater rating.

My mill motor, which uses brushes, now has a pair wired across the commutator. This completely kills the noise that used to come from it. I also fitted a mains suppression filter inside the control box. That one I salvaged from a dead computer PSU.

Fortunately non of the fluorescent lighting in the shop produce any interference. I've got a mixture of normal and electronic ballasted ones.

I used some cheap ceramics, 0.01uf, but 0.1uf or 0.001uf would probably work fine. You can get them from a number of places. Adafruit sells a ten-pack of 0.1uf's. Sparkfun sells a whole kit of different values, including electrolytics. I've gotten kits from Amazon. As previously mentioned, you could parallel a bulk electrolytic and a small ceramic, but a single ceramic in the head and the bulk capacitance on the TouchDRO board does the job for me.

The problem exists because the scales consume minuscule current so that they can run on a coin cell for a year or more. The high supply impedance of the logic chip in the read head makes it very susceptible to noise. The manufacturers can get away with no decoupling in the head because the scales are normally running on batteries and isolated.

Fiddling with the capacitance on Yuriy's TouchDRO boards might provide a fix, but I've seen long power supply cables cause nasty problems. I always decouple as close to the power pin of an IC as I can get as part of the overall power system design, which involves an array of capacitance types and values chosen to broaden the bandwidth of the power supply decoupling scheme. (I also always design with very low impedance power supply plane layers, but those design decisions have already been made for us here.)