Uncompressed the resistance will be higher. In the order of 25K Ohm.
Change the range on your meter. “1” is probably the over-range indicator.
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Hi, this was my result for each range
20k Ω - 1
200k Ω - 1
2M Ω - 1
20M Ω - 1
Should i just assume a number like 5 mil for example?
No, why would you assume such a low value?
You need a meter that can measure above 20k Ohm.
You are not measuring the resistance correctly then.
How should i do it correctly?
I can still get the resistance value when I’m on the bed and tuning to 20k.
But out of bed still gives me 1 (out of range) after tuning all the way to 20M
Do you have any known value resistors laying around greater than 2M ohm?
if you do check those and see if the meter returns the correct value.
maybe the meter is bad. Or maybe it needs a new battery?
I’ll try to get some 2M, and 20M ones.
I rarely use it but I’ll try replacing new batteries as well
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I ordered a sensor from Amazon that is 60 cm and looked similar but not exactly the same as ops. The range spec was 10g to 10kg. Without mattress, with mattress or with mattress and person on top of the sensor, the resistance was out of range with my multimeter set in the mega ohm range. Only if I am pushing directly on the sensor with my finger was I able to bring the resistance down to the 50k ohm range.
I wonder if it’s because my bed (memory foam) has really good weigh distribution so the sensor is not feeling any significant weight. My solution is to prop up the sensor by elevating it on the slates using a strip of ply wood. With that I am able to get sensor to produce a resistance of 10k ohm. I would suggest trying that to see if you can lower the resistance down that way.
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Updated the first post to use a number entity instead of an input number.
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Hi all, I’m trying to build my sensor. I already have all the components and have measured the resistance of the FSR in and out of the bed.
My values are .50 out of the bed and .25 in bed using the multimeter in the 2M mode.
With this values, what is the resistance value that I need to use? I’m pretty noob in electronics.
Any help will be really appreciated.
Put the numbers into the equation in the first post.
I bought a bunch of different round ones for another use but haven’t played with them yet.
I was planning on investigating if they could be coupled with a Xiaomi door sensor (but sounds like this is unlikely to be reliable, as per some discussions in this thread). I was going to try using them for seat occupancy.
I was thinking about trying to use one for bed occupancy, since I have a bunch of them. Perhaps one with the right rating may work ok. Maybe they could go under just your head etc? I guess they’re unlikely to work as well as a long linear one.
I bought from here with no problems.
AU $2.42 7%OFF | 1kg 3kg 5kg 10KG 20KG 30kg 50KG 100KG 150KG Film Pressure Sensor Resistive Force Sensitive Plantar Flexible Robot FSR Insole
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Thanks for the project idea, I just finished mine up and installed it this morning. I’m trying to keep everything zigbee so went with an aqara door sensor instead. It’s designed so I can pick up which side of the bed is occupied, but only had one door sensor on hand, so it’s tied together for now.
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Keen to hear how reliable this is with the Aqara sensor. Could you add a little detail about your battery upgrade too please?
I can’t speak to reliability; I just installed it today. In testing it has been 100% repeatable, triggers on my body weight but not the dogs, no false triggers and clears instantly.
Due to the low resistance when the FSR is compressed, I was concerned about battery life, with the stock battery I estimated the battery lasting less then 30 days with the voltage divider alone, not including whatever draw the door sensor has. With the CR123A it should be several years. They are both 3v, so it’s a 1 to 1 swap.
I used a LM393 as a voltage comparator, when the FSR is compressed the voltage to the LM393 increases which causes the output to pull the 1v line to ground on the door sensor which registers as closed. The set point can be adjusted using the 50K pot.
This is the circuit, half of it anyways, the LN393 has two channels, so I’m using on for each FSR.
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Great post. Quick question. I followed the instructions and my side if the bed there is no issues at all. But my partner is a lot lighter than me and sensor does not detect her at all when she is on bed. I put the sensor between mattress and slat box spring base. Any suggestions to get lighter folks with this set up ?
How did you choose R1?
With your weight or hers?
That is a good point. With mine. Maybe I should calculate it properly. I just tried higher and higher resistors but that was probably not a good idea.