Hi folks.
I have this instrument which has a moving arm in 3 dimensions. I will save you with the malfunction's symptoms, but I narrowed down the problem to a small pcb on the arm which has 4 photointerruptor sensors on to help with positioning the arm.
These 4 sensors are named Y home, X Sensor, Z Home, Z Sensor.
There are another couple sensors on the arm system on a different place than here, but the problem is on this particular pcb.
So here are some pics of the circuit itself. The schematic is quite simple and it goes something like this that I drew, as far as I could tell. Excuse me for not drawing it properly, but I am no professional
These sensors are fed on one side with 1.15V approx each and they interrupt the 5Volts that are to be read on the other side.
So when something is between the IR sensor and interrupts the lightpath, you have 5Volts reading on the multimeter.
One of those sensors display 5 volts all the time, even though there is nothing in between the ir transmitter and receiver... No response from them whatsoever...
Here is the confusing part. I tried swapping a working sensor with one that didn't work, and the problem remained where I put the "new" sensor. So the problem is in the particular positions of the circuit itself and not the sensor.
The resistors are used to drop the 5V voltage to 1.15V to feed the IR transmitter. The are 330 ohms and they measure correctly on the circuit with the multimeter. The caps seem to be leak free. When I put the leads of the multimeter one way I have infinite resistance and when I put the multimeter the other way, I measure 1433 ohms.
There is a 6 pin connector on the pcb as you see and it gets connected with a ribbon with 6 cables inside. These cables give all 5volts each and one is ground. The 4 pins with 5 volts are for the sensors, one pin with 5 Volts is for feeding the IR transmitters of the sensors and it is common for all sensors.
So when the 5Volts from one sensor get interrupted, the instrument reacts and understands the command. I tried short circuiting those 5Volts individually on the ribbon cable and the instrument responds to those signals. So the problem should lie on the pcb I guess, right?
I also checked the ribbon for bad connections etc, but all works well with it. It sits in tight and gives a good connection.
Could somebody chime in and give me an idea of what could possibly go wrong with this circuit. It seems quite simple and yet I cannot figure it out..
Thanks in advance.
I have this instrument which has a moving arm in 3 dimensions. I will save you with the malfunction's symptoms, but I narrowed down the problem to a small pcb on the arm which has 4 photointerruptor sensors on to help with positioning the arm.
These 4 sensors are named Y home, X Sensor, Z Home, Z Sensor.
There are another couple sensors on the arm system on a different place than here, but the problem is on this particular pcb.
So here are some pics of the circuit itself. The schematic is quite simple and it goes something like this that I drew, as far as I could tell. Excuse me for not drawing it properly, but I am no professional
These sensors are fed on one side with 1.15V approx each and they interrupt the 5Volts that are to be read on the other side.
So when something is between the IR sensor and interrupts the lightpath, you have 5Volts reading on the multimeter.
One of those sensors display 5 volts all the time, even though there is nothing in between the ir transmitter and receiver... No response from them whatsoever...
Here is the confusing part. I tried swapping a working sensor with one that didn't work, and the problem remained where I put the "new" sensor. So the problem is in the particular positions of the circuit itself and not the sensor.
The resistors are used to drop the 5V voltage to 1.15V to feed the IR transmitter. The are 330 ohms and they measure correctly on the circuit with the multimeter. The caps seem to be leak free. When I put the leads of the multimeter one way I have infinite resistance and when I put the multimeter the other way, I measure 1433 ohms.
There is a 6 pin connector on the pcb as you see and it gets connected with a ribbon with 6 cables inside. These cables give all 5volts each and one is ground. The 4 pins with 5 volts are for the sensors, one pin with 5 Volts is for feeding the IR transmitters of the sensors and it is common for all sensors.
So when the 5Volts from one sensor get interrupted, the instrument reacts and understands the command. I tried short circuiting those 5Volts individually on the ribbon cable and the instrument responds to those signals. So the problem should lie on the pcb I guess, right?
I also checked the ribbon for bad connections etc, but all works well with it. It sits in tight and gives a good connection.
Could somebody chime in and give me an idea of what could possibly go wrong with this circuit. It seems quite simple and yet I cannot figure it out..
Thanks in advance.
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