Can I change the display on a digital scale to a LED?

Would it be possible to make a digital scale turn an led on or off instead of showing a display of numbers. So instead of showing the weight, the light would turn on, and when the weight was zero, instead the light would be off. Any help would be great thanks

This could be really complicated, since you'd need to dig into the circuitry inside the scale to find the signal that is relative to the weight on the scale. Unless you are skilled with in-situ debugging, I'd recommend a different alternative.

What are you trying to determine by using the scale? The presence of someone/something on a platform? If you give us some context, the folks on the forums might have some different parts that may work better (piezo discs, linear potentiometers, pressure transducers, etc).

hspender said:

Would it be possible to make a digital scale turn an led on or off instead of showing a display of numbers. So instead of showing the weight, the light would turn on, and when the weight was zero, instead the light would be off. Any help would be great thanks

Click to expand...

It may be possible but the hardware and the firmware also needs to be modified which may be compared to the design and development of a new project.

thanks, basically what i want to do is use a sensitive pressure sensor of some kind to measure whenever something lands on it, and this would then turn on a light. I have looked at peizo electric stuff and as far as i understand although i could be wrong, they only release a signal when there is a change in pressure, while i need something that would leave the light on for the entire time something was placed on it. Also ontop of that it would be ideal if the sensor was small, around 5cm x 5cm or smaller.
Could i place a pressure transducers under a plastic sheet, and then whenever the pressure increased the resistance would change and stay that way until the pressure was removed, because that sounds ideal

hspender said:

thanks, basically what i want to do is use a sensitive pressure sensor of some kind to measure whenever something lands on it, and this would then turn on a light. I have looked at peizo electric stuff and as far as i understand although i could be wrong, they only release a signal when there is a change in pressure, while i need something that would leave the light on for the entire time something was placed on it. Also ontop of that it would be ideal if the sensor was small, around 5cm x 5cm or smaller.
Could i place a pressure transducers under a plastic sheet, and then whenever the pressure increased the resistance would change and stay that way until the pressure was removed, because that sounds ideal

Click to expand...

How heavy is the object you want to sense? I would maybe try something as simple as a snap-action switch with a long lever. The target area could be a pad located at the end of the lever. Something like this...
Digi-Key - 480-2321-ND (Manufacturer - 311SM703-T)
or
**broken link removed**

Start here for all of the snap-action switch options.

The switch would be super-simple... battery, switch, resistor, LED, done.

The pressure transducer could be a good alternative, then you'd need to add additional circuits to look at the output voltage/current of the transducer and compare it to a threshold level. A comparator, or an op amp set up as a comparator, driving the LED could work... depending on the output from the transducer.

Hspender you say when something lands on it - A gnat?, a gain of sugar, a baseball? is it a high speed event?
having said all that, i think a good way to go is to get a ready made LED + opto transistor proximatey unit. This is a LED + opto transistor in a housing so they are opticaly aligned with a slot cut in the housing between the two. If the LED is powered the opto transistor will be switched on. As a piece of lightproof material is introduced into the slot, the opto transistor goes linear, and it start dropping more and more voltage across, until the slot is completely filled and the opto transistor is off and the full +Vcc appears at the output.
So if you have a springy beam (think of a ruler) with a little tab hanging under it, as its weighted down it will droop and the tab will cut of the light to the opto transistor. This system can be made extremelly sensitive ,depending on how much amplification you use.
Frank