Microgram scale

Hello

I want to read out micrograms of a scale. As I read on the forums, buying a simple microscale should do the trick.

I bought a microgram scale (very cheap). And opened it, got the components out of it. I try to figure out what to do with it. I took some pictures:

First Image

This is an overview of the components. On the left is the scale, on the right is the controller (with LCD, LED and 2 buttons on the back)

Second Image

This is a close up of the wiring. From left to right: -Black wire to LED -Red wire to LED

-Black wire to scale -White wire to scale -Blue wire to scale -Red wire to scale

-Red wire to battery (-) -Black wire to battery (+)

Third Image

This is a picture of a label behind the LCD and LED (LED is removed here) But googling that label gives me nothing.

Now the main question, what is the best approach to read out the scale data to Arduino?

Thanks a lot

Pictures are not very helpful, or how would you determine from the picture of a PC, what it is doing just now?

You need a datasheet of your kit, including an application note. Ask you dealer, or look around on his website.

Hmh Ok thanks, It is a Jennings JZ115 scale. I cannot find a datasheet somewhere, is there a way to determine what components that are used? Maybe I can find a datasheet of those components online.

You see that 8-pin IC? That is (probably) the amplifier. You will need that or something like it.

But to answer your original question of “what is the best approach to read out the scale data to Arduino?”, get a scale with serial output.

Red / black to loadcell is probably power. Blue/red are outputs from the bridge. The voltage differece needs an amplifier. -> Hx711 or other precition intrumentation amplifier like the INA... OPA... (there are several..)

Microgram?

Carharttguy: It is a Jennings JZ115 scale.

I think you mean centigram.

Paulcet: You see that 8-pin IC? That is (probably) the amplifier. You will need that or something like it.

I doubt that. From experience the amplifier/LCD/etc. chip is a chip-on-board thing and then hidden underneath that epoxy blob. I've only disassembled a couple scales but there was never amplified output available anywhere on the board; maybe a few years ago with older chipsets but not with the cheap scales of today.

The simplest way forward is to cut the wires from that PCB and then buy an HX711 module to interface with the load cell (like Knut mentioned). Don't get an instrumentation amp like the INA125P, etc. though; that's a much more complex and expensive way to go.

Hello people

I kind off forgot this topic. I was searching this week for data sheets, even using this kind of sites to get the brand of the loadcell: http://tswa.com/tools/loadcellcolors.htm

I was thinking the same that Red/Black is power, because that are the same colors that are used for powering the LED.

Thanks for the Hx711 tip, I wasn't aware something like this existed. I found one on DealExtreme: http://www.dx.com/p/hx711-weighing-sensor-module-green-384154#.VVSnzBfrRmo

Now my next step is to figure out how this works, but there is much information about this on internet. I'll keep you guys updated in this post. (could be a good start for other beginners like me)

choose a shielded version HX711 http://www.ebay.com/itm/HX711-Dual-channel-24-bit-A-D-Conversion-Weighing-Sensor-Module-Metal-Shied-/281410718606?pt=LH_DefaultDomain_0&hash=item418562cb8e

knut_ny: choose a shielded version HX711 http://www.ebay.com/itm/HX711-Dual-channel-24-bit-A-D-Conversion-Weighing-Sensor-Module-Metal-Shied-/281410718606?pt=LH_DefaultDomain_0&hash=item418562cb8e

Ok, why is that better?

It is shielded from electromagnetic noise! Even fraction of a mV will change reading. (for gain 64, each step is 5 nV)

knut_ny: It is shielded from electromagnetic noise! Even fraction of a mV will change reading. (for gain 64, each step is 5 nV)

Have you actually compared the shielded versions to the unshielded? I'm not challenging your advice; certainly makes sense that the shielded version would be preferred, but just asking if you have any experience with both versions side-by-side.

I have used the shielded one only, with shielded connection wires. The fluctuations in reading decreased when the metal covers was mounted.. and even more when shieldes cables was used.