So, I posted this here because it isn't really Arduino related to an extent. Just thought I'd pick up some idle suggestions if anyone felt like giving them. It's more of a design problem than a troubleshooting/technical problem. Here goes...
I've got this digital fish scale. The pocket kind you might take to the lake to weigh anything you catch. Basically it's got a hook on it, you turn it on, put your fish on, and the scale tells you the weight. Pretty nifty.
As an added bonus, it has an automatic shutoff that powers the unit down after thirty seconds of inactivity. However, I've been puzzling lately over how to disable this feature. (in case you're curious, I'm not using the scale for weighing fish. It's going into an Arduino robot)
My idea was to provide a very tiny, varying voltage across the pin on the scale that is responsible for detecting the changes in the mechanical part of the scale. I'd do this with an Arduino pinout and a resistor network of some sort. If I apply some little voltage that varies slightly, it seems like the scale will 'think' there is always a small varying weight on the hook. Hence it will be active and won't shut off. Of course, this will introduce some error into the final weight measurement (if it even worked), but that's not really too big of an issue, I think.
This is my attempted solution, but I was curious as to what some other more savvy folks might try. Feel free to comment on the plausibility/implausibility of my idea as well as offering some of your own. I will be tackling this problem in the upcoming week, but this post is more for discussion than finding an actual, concrete solution.
I guess my first question would be what is the use of this in the robot? Could it be off until needed and then turned on and read then allowed to turn off again?
Does the scale use a momentary push switch to turn it on? If so I've seen similar projects that wire the contacts of a small 5 volt reed relay across the built in switch. Then the micro-controller could power the relay coil momentarily to keep the scale alive. Just a thought.
Your idea of injecting a voltage into the scale does sound like a very hit or miss situation as it's bound to saturate the measurement circuit and cause crazy measurements until it's removed.
I guess my first question would be what is the use of this in the robot? Could it be off until needed and then turned on and read then allowed to turn off again?
The scale is being used by the robot to weigh an object. The Arduino could send a signal to the scale right before the object needs to be weighed (this is all happening autonomously, BTW). However, the scale may need to be tared as well. So, just sending a power on signal may not be sufficient enough. Thanks for the suggestion, though...it seems like it would be the best bet if it wasn't for the scale needing to be tared.
Does the scale use a momentary push switch to turn it on? If so I've seen similar projects that wire the contacts of a small 5 volt reed relay across the built in switch. Then the micro-controller could power the relay coil momentarily to keep the scale alive. Just a thought.
Yes, the fish scale does use a momentary switch to power on. I like this idea. It seems like this way the scale could be turned on and left on. I'm wondering how to work in taring capability if it is necessary, though...either way, this seems like a start.