# Tilt Sensor - Critiques?

Discussion in 'The Projects Forum' started by sjgallagher2, Aug 19, 2013.

1. ### sjgallagher2 Thread Starter Member

Feb 6, 2013
121
8
This one's simple. My brother and I love longboarding, but when looking for new hills, sometimes it's hard to tell if a hill is good or not. So I built a circuit that will do the trick:

It works with a variable voltage divider hooked up to an op-amp acting as a comparator. The trick here is that the pot in the diagram is in the car, sideways, with a little weight solder to it. As the car becomes angled from flat ground the brush stays in the same spot (the weight pulls it down) while the body of the pot is turned with the car. In that circuit above the pot has to be at 54 degrees in order for it to be declared a "good hill" which is totally outrageous but it's mainly for example so suspend the disbelief at this point As far as I can tell the problems might exist with the output low voltage of the comparator being 0.8V usually (enough to bias the LED), which I sorta fixed with a voltage divider, and the potentiometer is being really underused, seeing as it can turn 270 degrees and it will probably only be turned 15 degrees ever. I can live with it, but it's not optimal. The last issue is how to put it in the car, in a non permanent way... any suggestions are welcome. The best weight is also an issue, but I think solve that.

So what do you think of my circuit? Is there a better, simpler way? Can you think of a better way to reduce the low output voltage? Is there such a pot that will only turn 30 degrees? Thanks -Sam Gallagher

2. ### #12 Expert

Nov 30, 2010
17,831
9,162
It looks like as good as it's going to get. You could put a common 1N4001 in series with R3 to jack up the start voltage of the LED, but you would still need a grounding resistor to pull a little bit of current through the diode. No need to add a part to get where you already got to.

And, no. There aren't any 30 degree pots. Look at a wah-wah pedal to see a mechanical gear system to make 30 degrees of movement move a pot by 180 degrees. Still, the op-amp is plenty sensitive enough to work with a 30 degree range of movement. No need to add parts to get where you already got to.

3. ### sjgallagher2 Thread Starter Member

Feb 6, 2013
121
8
Thanks for the response! I agree, it'd be a lot of work for a problem thats not really a problem. I just built the circuit, it looks like it's going work perfectly.

Feb 27, 2010
235
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They make 30deg tilt sensors... It would be far more reliable then a weight rigged to a pot.. .

5. ### tubeguy Well-Known Member

Nov 3, 2012
1,157
197
Yes, but sometimes isn't it fun to come up with a creative solution using only what is on hand ??

6. ### THE_RB AAC Fanatic!

Feb 11, 2008
5,435
1,309
Like a mercury switch and a LED?

7. ### strantor AAC Fanatic!

Oct 3, 2010
4,591
2,473
or a bubble level? - taped @ 30° (or 54° or whatever a good hill is) inside the car?

#12 likes this.
8. ### wayneh Expert

Sep 9, 2010
13,427
4,268
Or one of these.

• ###### Protractor.jpg
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Last edited: Aug 21, 2013
9. ### tubeguy Well-Known Member

Nov 3, 2012
1,157
197
You could attach the circuit using a strong magnet. A nice flat steel surface works great.

10. ### wayneh Expert

Sep 9, 2010
13,427
4,268
The protractor above has a magnetic base.

11. ### tubeguy Well-Known Member

Nov 3, 2012
1,157
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@wayneh
I don"t see any attachment in post #8. ??
Do I have a glitch on my PC ?

12. ### wayneh Expert

Sep 9, 2010
13,427
4,268
Huh, it was there last night but this AM I couldn't see it either.

13. ### Bernard AAC Fanatic!

Aug 7, 2008
4,533
476
RVers sometimes use a large bubble level, could easily make one with clear plastic tubing.

14. ### Metalmann Active Member

Dec 8, 2012
700
224

I have 3 or four of those for fabrication, and the magnets aren't very strong for a moving object, if that is what he uses it for. They are fine for stationary fab work, though.