#11

That is using it with a pull-up resistor... It will work without one however (I have used them without a resistor so I can confirm that it does work sans resistor)... Remember they are basically a variable resistor all by themselves... Since you were going to use it in a go/ no go (on/off) situation I figured you weren't looking to use them linearly..... However, a 10k resistor will give it more stable (linear) readings. I am not sure if pin "float" happens on the analog ports of the ezb, but I do know it happens on the digital ports... A pull-up resistor will control any pin "float"...

#12

That's great to know. Thanks Richard. So a little trial and error to help dial the readings in to what I need, and all should be well. I have a few 10k resistors knocking around should I need to use them for reading stability as you mentioned.

Thanks again. Smile

#13

@Dave depicts 2 different ways to use the flex resistor... The first on has it using a 10K resistor to pull high. The second picture with the arduino shows a 22K resistor and the flex being pulled low... You'll have to see which one works better.... One way may work better than the other... I have only used these with my old V3 so I am curious how the 3.3v ezb4 analog port will affect how they preform....

#14

Humm, good to know these can be used without a resister.

Yes, I'm also looking forward to seeing how this works for you also. There are lots of uses for these. I've read that the readings from them are a bit hard to read if you use them for linear readings. Seems they read slowly at first and then when they get to the last 20% of the bend they really take off.

Readings from the ADC ports on the EZB do float badly. I'm using all of mine as an on/off (high/low) switch so it's not an issue with me. I've been wanting to add a pull up resistor to one just to see how well it stabilizes it.

#15

That's cool. I'll have a play around when I receive them and post the results. Over the next week or two I'm going to strip out K-9's entire electrical system to re-wire/retrace everything, add additional sensors (hence the flex sensors), replace the damaged acrylic panel, and give him an Acer W3 tab for his display screen.

#16

Lucky dog! Smile

#17

Tell me about it, lol. Well he has been a good boy so he deserves it. Winky

#18

A bit of an update in regards to the flex sensors. After a couple of weeks break after receiving some very bad news regarding family issues, I've got back to robots to take my mind of things. Anyway, I got home today and found that the sensors had arrived. But unfortunately the happy feeling soon went away after I hooked them up to my v4.

Using an ADC reader set at 100ms update time, I first tried wiring one up just using signal and ground pins on an analog port. With the sensor flat, the noise reading fluctuated quite a bit between 0 and 7, and bending the sensors didn't make any difference.

I then tried the way that was documented on the website using a 10k pull up resistor (as they recommended). I ran the Vcc through a 5v regulator to a digital pin, and tied in the 10k between the ground and signal wires and ran them to the ground and signal pins on an analog port. It reduced the noise (readings between 0 and 4, mostly between 0 and 2), but flexing the sensor made little to no difference whatsoever.

So unless anyone has any other ideas, I think I just blew $60 (3 sensors, shipping, import tax) on something I can't use. So I might look in to one of the ideas Richard or Dave mentioned. Kinda sucks though, not just for the waste of cash, but these would have been ideal with easy fitting to the bumpers. *mad*

#19

Hmmm @Steve G you should definitely get some response on the ADC, instead of 5V I would tie the 10kohm pullup resistor to 3.3V. The ADC pins are 5V tolerant but can only read a voltage between 0-3.3V.

Reading the specs it looks like the resistance changes from 10kohm to 20kohm when flexed. So initially if you are using a 10kohm pullup you should see a value of 1.65V on the ADC port and when flexed the voltage should go up to ~2.5V.

Please check if your solder joints are good on the sensor itself or double check if the correct ADC port is selected.

#20

@Jeremie.

Thanks for the reply. I can confirm that the solder points are clean and well attached using a solder/flux mix (which I use elsewhere with good results). And I defiantly had the correct port selected from the config menu. The only voltage it was reading was flutuating between 0 and 0.2v at the most when either flexed or straight. I even tried different ADC ports just to be sure. I can try using the 10k on 3.3, but the documentation was using an Arduino on 5v on their example so I would have expected it to work.