Resistive fabric + buzzer

Hi,

I’m new and haven’t got an arduino (yet).
Please don’t shoot if i’m in the wrong forum.

I’m trying to get a buzzer/vibrator (no not what you think) go off once a piece of resistive fabric is either stretched beyond a certain point, either goes slack.
The idea is also that i should be able to only make it work at certain times e.g. during 15 min every hour or so.

I would also like to be able to configure these parameters: at what measured resistance/beyond what stretch or slack should the buzzer go off and what is the time interval it should work.

Is arduino (lilypad?) a good solution?

Could anyone give me a nudge in the right direction to start this project? Materials needed, input, output… any help is more than welcome!

Thanks!

Oh, i’m on Mac, don’t know if that’s of any importance for arduino.

Jonathan

Hi Jonathan, and welcome to the forums

Do you have a sensor in mind for this? I'm not sure what you mean by resistive fabric, so if you have an example that would be great. But if you have the sensor sorted out then the rest of what you're looking to achieve is quite simple to do with any Arduino, including the lilypad or flora types.

Do you need it to be active for 15 minutes then wait an hour before being active again, or do you have a need for it to know the time so it will start at a particular time relative to the hour? If the 2nd, Arduino doesn't know the time itself so you'd be looking to add a RTC (Real Time Clock) module. If it's just elapsed time since the most recent trigger that you need to act on, Arduino can do that without additional hardware.

There is an Arduino IDE for Mac so you're good to go.

Cheers ! Geoff

HI Geoff, thanks for replying!

In the meantime, I have been doing some googling around and it appears I can find some ready made stretch sensors. The resistive fabric I'm looking at is this kind: HOW TO GET WHAT YOU WANT

As for the timer, I don't need real time, just calculating time so no real time clock. I suppose the time interval is easily modified in a sketch.

I'll go ahead and get the arduino. Is it ok if I get back to you once I have it?

thanks again!

Jonathan

If you keep your questions in the forum we all learn with you. Looking forward to seeing what you're developing here.

Cheers! Geoff

Hi Geoff,

The project had been on a stand still for a while, but I'm picking it up again.

So, I'll be wanting to measure the resistivity in the range of 20-200 Ohm. When a threshold will be reached I'll want a buzzer/vibrator to go off.

Additionaly, I'll want to monitor this during certain periods of the day, so say every 30 minutes I will want to measure the resistivity during 10 minutes.

Also, I would be interested in knowing what Arduino kit you would suggest me to get. I was thinking of a lilypad as the user will wear the device.

Thanks.
In case you wouldn't read this anymore, I'll post it as a new topic.

Cheers,

Jonathan

P-Works:
Also, I would be interested in knowing what Arduino kit you would suggest me to get. I was thinking of a lilypad as the user will wear the device.

Well, actually, there is virtually no difference between a Lilypad and a Pro Mini without its headers soldered on. The Lilypad has two main purposes, to facilitate connections made by sewing with conductive thread, and to be deliberately decorative. If you do not need either of these functions, just use a Pro Mini (though you might need to disable the regulator and pilot light).

Clearly if you are operating from batteries, you will need to minimise the standby current. You will need to consider using sleep modes. If you are to measure resistivity in the range of 20-200 Ohms, you definitely do not want to apply current continuously to make measurements, so you need to use two pins, one with the sensor material to ground, and a second with a resistor (perhaps 470 Ohms) to the first to measure current only when that second pin is pulled HIGH for a couple of milliseconds to make the reading.

The batteries could be either a LiPo rechargeable, or a pack of three alkaline AA cells.

Thanks Paul,

I’ll go ahead and buy a kit. Will come back once the project is more advanced for advice on the circuitry.

Thanks!

Jonathan