Industrial Control PCB Mounting
For the new design of PCB circuit board, debugging will often encounter some difficulties, especially when the circuit board is relatively large and components are relatively long, it's often unable to start. However, if you master a reasonable method of debugging, debugging will be twice as effective.
For the new PCB board just done, we should first check whether there are any problems on the board, such as whether there are obvious cracks, whether there is a short circuit or open road.If necessary, check whether the resistance between power wire and ground wire is large enough.Then do component installation.For independent modules, if you're not sure they work, not all devices are good, but partially installed (a smaller full installation for circuit), so it's easy to determine the scope of the failure and the problem, not knowing how to start.
Generally speaking, the power part can be installed first, and then energized to check whether the power supply and output voltage are normal.(if you're not sure, it's recommended that you add a fuse, just in case.)Consider using an adjustable voltage source with current limit.The preset current is superior to the protection current, the voltage of the stabilized voltage supply slowly increases, and the input current, input voltage and output voltage are monitored.If there is no overcurrent protection, etc., and the output voltage has reached normal, then the power supply is OK.Then turn off the power source, find out failure points, and repeat the process until the power source is normal.
Then install the other modules gradually, each with a good installation, electrification test, and avoid overflows and burn-down components caused by design errors and/or installation errors when the power supply conforms to the above steps.
There are usually several ways to find errors:
1. Voltage measurement
First, verify if the voltage of each chip power pin is normal, then check if the reference voltage is normal and if operating voltage at each point is normal.For example, when the silicon triode is conducting, the BE junction voltage is about 0.7v, while the CE junction voltage is about 0.3v or lower.If the BE junction voltage of the triode is greater than 0.7v (except for special transistors such as darlington transistor), the BE junction may BE disconnected.
2. Of course, there are many other ways to find errors, look, listen, smell, touch and so on.
"Look" refers to seeing elements without obvious mechanical damage, such as rupture, combustion and deformation;"listen" is to listen to if the working sound is normal, such as when something does not ring, sound does not ring or sound is not normal;"Smell" is to check for odors, such as odors and electrolyte capacitors.
3. Signal injection method
Add the signal source to the input end, and then measure the waveform of each point in turn to see if it is normal, so as to find the fault point. Sometimes we will use a simple method, such as tweezers, input to all levels will touch, and see if the output response is used in the audio and video amplification circuit (but note if the heating circuit at the bottom is high-voltage circuit, can not using this method, otherwise it may cause electric shock).If there is no reaction before the strike, and after the level reaction, it indicates that the problem is at a higher level and should be focus on it.