I'll be back whenever you need !
Did you add the capacitor in the end? The Sharp documentation calls for one and everywhere I've seen that sells this sensor states it is required.
Help the sensor 30 cm from a white pad and the reading are really up and down.
Also when i mover the sensor closer to the paper the vale goes up and not down??
Be careful, the scale of the frame is automatically reduced when the signal is of low amplitude (automatic magnifying glass effect), in order to have a curve that is well displayed; on the drawing it evolves between 32 and 36, which is low (values with no signification, they are not cm). If you cause a sudden amplitude, you will see the thickness of these fluctuations reduce instantly. There are still too many fluctuations on your curve, maybe the stability of the USB power supply is not sufficient... a capacitor should improve the curve and reduce the fluctuations even more, as says gibbobaz.
Yes, when the distance is small (less than 5 cm), weird things happen for me too. I think the sensor works well beyond 5 cm.
If you want display cm on the curve, put in comment (add //) the line
// dis = 51 - dis;
but the curve will be inverted...
Have you tried to set A0 to Gnd, and run the serial terminal? you will get the distances displayed in cm
Morning Pat. I have been away racing this weekend s not had time to play. I will have a go after work and let you know how i get on. Thanks
Good morning.
I have tried the sensor on the fork leg and i dont think the IR is the way to go. With the silver fork leg the readings was all over and when i pushed the fork leg down to a position the reading wasn't accurate.
I would still like to try and use a magnetic linear encoder. I would be able to run this along side the front brake cable and would be up and out the way to prevent damage.
I have looked around and found a this. Would it be possible to use a magnetic strip and only pick up on the 5mm pole length?? (Poles switch over)
Just to give you an idea. This is the standard way a front brake cable is routed on a motocross bike.
The cable passes through a small slider to keep the cable close to the front number plate. If i could get the magnetic strip to work with the cable this would be great.
I managed to get a some slow footage of motocross suspension in action. These are the top lads with good suspension set up and you can see how there handle bars are almost flat as the front wheel takes on the bumps
Pat not sure if you have seen the post about a magnetic linear encoder? Is this something you know about?
Iv emailed a few more company's but i think because i don't understand them they are not very helpful.
On large disk drives in the 80’s, they used a ribbon with a gray code printed and two optical sensors to detect/determine positioning of the disk head carriage… certainly good to sub-1mm.
It doesn’t have to be glass as they were, but the idea is valid.
Keep in mind the thermal stability of any solution you end up choosing. The longer travel, the larger chance of accumulated error from the media.
Hi lawton74, Hi lastchancename,
I also thought that the IR which diffuses in a cone from the emission LED could induce measurement defects (with the parts of the fork which are close to the IR emission-reception area), this is confirmed... I wondered if including the sensor and its target in a tube could solve this problem, but I don't believe it. Well, this sensor was a good experiment, maybe it can be used later?
I saw the magnetic strips given in link, but you also need a sensor adapted to these strips, and these materials seem rather adapted to a protected environment, maybe less to a motorcycle ?
Yes, all these sensors deliver information in a known way: either pulses (incremental encoders), or position values (absolute encoders), there is no difficulty to exploit them, except the acquisition speed which must be sufficient, for the 10 m/s of fast shock.
I saw the video !
Why not try a simple potentiometer, with a return wire ? easy to buy, cheap, to make tests ? even if it will not live several races (we can replace it), it will allow to make quick tests. I believe it will give good results, and curve variations that can be used.
This will allow you to settle the questions of mechanical installation, battery supply, and you will have the first results of curves; then, it will be enough to replace the potentiometer by a magnetic sensor, and to change the program, but all the mechanical part will have been solved.
Moring Pat.
Im sure the IR sensor will become handy one day for another project.
I have been in talks with a company about a magnetic encoder and sensor. I'll add the reply back into this thread.
'' Hello Andy
Thankyou for your enquiry
We can offer linear encoders /potentiometers and offer 5v signal.
To clarify, please can you confirm the stroke length (measuring length) required is 310mm? (The over all length will be longer).
Step increments of 5 or 10mm would be unusual.
As you are using an Arduino, Could you use an analogue input, as the unit has a 10bit A/D converter is built into the device and possibly simpler than trying to analyse digital pulses.?
we can offer 0-10V outout trnasducer. Potenziometri PNSV - PN2SV - PN231V (elap.it) or we can offer a potentiometer 10kΩ, though I’m not 100% sure what current the Arduino can handle and therefore if a potentiometer is suitable?
In all cases, these are limited to 5m/s.
Within a linear potentiometer or transducer there are seals and wearing parts which limits the operation of these for dynamics.
Could you work with a linear encoder?
This will offer a pulse output, we can offer MSK4000 for example, this can work almost to <15m/s. so offers the speed required.
The resolution can be tailered, but at lowest resolution is 2mm
Operating voltage is 5V.
This requires a magnetic tape, which is easily cut to length. The benefit of this system is there is no contact and so potentially no wearing parts if the tape moves.
If the sensor moves, then the cable does have to contend with the cycles.
We can supply magnetic tape in 1m or longer lengths as one reel to be cut to desired length.
data-sheet-msk4000.pdf (siko-global.com)
Please let me know your thoughts''
I first looked into a potentiometer (gas strut style) but the price for a 300mm one was expensive and also i had the worry if anything would slightly bend the rod it could cause some big damage to the fork legs or go into the front wheel.
I thought about a strip that could run inside the fork guard and a spring connector that would run up and down a copper strip and use the resistance for a reading. The only problem then is you don't really have the true position.
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