The frequency of the generator’s output wave can be calculated with this formula :
f = 1.44 / (( R1 + 2 * (R2 + Rpotentiometer)) * C3 )
Therefore, the accuracy of the generator’s output wave frequency will be dependant of the accuracy of the parts above (R1, R2, Potentiometer and C3)
Hi bdaouas,
Thank you for posting this. From your knowledge, if there are (2) different am perimeter wires (a robotic mower and an underground pet fence), is there a way to try to reduce interference if I need to run one across the other at 90 degrees in (2) different places?
I don’t know the frequencies that either of them use and don’t think either allow changes.
If by interference, you mean crosstalk, you shouldn’t have electromagnetic interference issues since your two perimeter wires run one across the other perpendicularly. Crosstalk usually happens when wires are run one next to the other in parallel.
Hi,
I have an issue with this module. I think that @jcf was right. I explain my problem:
On the first module I bought, I had one sensor with good behavior. The second one saturates at maximum value, even when the sensor is far from the perimeter cable.
I have analysed the situation on most of the pins to verify what was happening. I saw that after first stage of amplification, an offset exists and this offset is amplified by second stage up to saturation.
I have bought two new kit. For first kit, the second sensor was working properly, but the first one was saturating.
on the last kit, both sensor are saturating.
I verified all continuity, everything seems to be clear.
The comment of @jcf points a lack of high pass filter between both amplification stage. Unfortunetly it seems to be difficult to adapt the board for that. I intend to test it on a new kit.
I am a bit surprised being the first to have this problem. Could something else explain my problem?
I purchased and assembled an arduino, a motor shield, the signal generator and sensor kit, and a robot chassis with motors and wheels, and I am now developing the sketch and testing the circuits…and I’m new at this. Rather than a perimeter wire, I plan to make this into an inductive guidance/wire following robot. Using the analogread function, I’m getting a scrolling readout same as listed above (400-780), but this raises 2 questions:
-
Why do the readings only fluctuate when the sensor is practically touching the signal wire? I thought this would start fluctuating within 15 cm of the wire.
-
I thought the raw values were to vary from 0 to 1024, according to the guide, but the scrolling example above and my own date show 400-780. What am I doing wrong?
I have not adjusted the potentiometer on the generator since I don’t know what I’m looking at.
THANK YOU!
I answer to myself:
I bought some other quad-op amplifier with the same pinout. I have built one of the module with a support so that i can exchange the amplifier easier.
I have tested .
one other LM324N works very well.
Other amplifier have similar problems. So I realy think that @jfc is totaly right. First stage creats an offset wich is amplified by second stage.
It could be a nice idea to propose an update adding a filter between the two amplification stage.
anyway, thanks for your work !
Hi,
I’m actually facing on the same problem.
I try to figure out how to remove this offset.
Because of this, the output signal of the second stage saturate at 5v.
Any idea of some value of filter between to stage?
Thanks
I am not very experienced in that, but I would say that a high pass filter with a limit at 100hz could solve this issue. This is far enough from the module frequency (>30kHz) and high enough to be sure that any constant value will be canceled.
Before second amplification (5 and 12 on wiring diagram) we have to had a capacitor and a resistor (eelectronique.aop.free.fr/AOP_lineaire_F/Filtre_PHaut_2.html) so that Fc = 1 / (2.pi.R.C)
Yes, I already do this but if I remember it’s not work well. I will test again (I think my previous Fc was about 1kHz) with lower fc.
Yesterday I found another way to do this (in theory) so I will test it too.
I am having the same problem. Were you able to solve the problem? If so, how? Thanks!
Same problem hete. Any news?
Do you have a photo of what the whole thing looks like all together on a robot because I’m confused about where to put everything and what I need so I photo might help
Hello everyone,
I just bought the sensor kit and I was very happy to have found such a nice and easy to use kit. After soldering (unfortunately there was already a capacitor missing but luckily i bought two kits so i took the one from the second kit) I tried to connect the sensor to my arduino and check the values. But my serial monitor only showed numbers in the range of 780 even after holding the inductor directly to the perimeter cable. My question now is what could I have done wrong. I am 100% sure I’ve soldered everything correctly. I also tested every possible state of the potentiometer while holding the inductor over the cable. The values didn’t change. Did anyone have the same problem or has a possible solution for me? I’m really struggling because I can’t imagine whats wrong other than the NE555 or the amplifiers being broken but I don’t know ow to check this. Thanks in advance for anyone trying to help me.
I had wanted to buy the kit but postage was expensive. I have a landroid and wanted to have several loops in different places. Earlier it said there was no way to know whether the robot mowere was in or out of a loop. However,Some / Slow progress | Details | Hackaday.io gives some insight into this though I do not understand it. There seem to be more than one sensor in landroids or some of them. How to check wire's sensors on Landroid
If someone could explain how this works it would be great.
I notice that the output signal from the NE555 timer is a square wave. However when the output on pin 3 goes through the RC circuit it creates a signal that undergoes exponential decay. I was wondering if this was intentional or if I have done something wrong. I can still sense the wire with the receiver. Wondering why the resistor and capacitor were added to output. Was it to limit current?
Hi all. I couldn’t get a 4.7 K potentiometer. Is it ok to use a 5k one instead? Thanks
Sorry to sound naive, but from the drawings, I can’t see if you are using the inductor as an aerial or if the small copper coil - which appears to be parallel to 1mh and C couple - is the aerial.
I have found this kit very useful in making an RC car drive around the yard autonomously. However, I’m getting about 10cm of wire sensing range which is insufficient to drive at the desired speed. Is there any way to increase the range? Maybe a FET being driven by the 555 timer? Or an additional op-amp in series on the receiver?
Also, what is the purpose of the C5 capacitor on the generator?
Thank you!!!
has anyone tried to build it? it works?
hello, first of all I just want to thank you for putting together this awesome project , second of all I’m taking a wak at it but I made some modification and I would love to hear your thoughts on the subject.
the LM324 worked great but it saturates at 4V on my circuit so I replaced it with a rail to rail OPamp , I also added an integrator circuit on the output to make it output a DC signal that made it easier to use.
I changed the amplification values on the sensor board and added resonance by adding a capasitor to the generator board wich increased the signal detecting zone.
one last thing I added 2 potentiometers to the sensor board to precisely calibrate the amplification .
do you think any of this was a good Idea and why. and what else would you like me to try.
thank you again this was lots of fun and I’ll let you know how the final product came out once Im done.