RG1R DL Automation For Swing Gates
Today I got an automation electronic motherboard (mobo) from a technician who setup swing gates. The mobo has a failure on two relays. The relays wont work, as they are bad and the swing gate motor have trouble to close and open the gate.
So I decide to check what type of electronic it is and how can I repair. Here is the mobo and I made a small description about how this mobo is designed:
The motor controlling section:
In this area there are the main parts are the four relays. They control the gate swinging motor. Under each relay is one protection diode, this diodes could be a reason for a not working relay, but in my case they are fine. In this section you have also a fuse for protecting the circuit from over current flowing if something goes wrong in the motor or the electronic.
The power section is a simple stuff build up from two main parts.
1. LM317 adjustable voltage regulator
2. 78L09 smd +9V, 0.1A voltage regulator
This section could cause a major problem because the CPU is powered through this section. If the CPU won’t start then all the I/O section won’t work. Actually the whole thing would be dead.
The I/O area:
This is the section where info goes out to the motor how to manage the gate moving, and info come in from the sensors on the gate. Gate closed, opened, gate blocked etc… Actually, if something would be wrong on this section, the gate could have a strange behavior.
The gate could non-stop open and close or the worst think would be if the control section didn’t got an info does your car is on the half way in or out and the gate would smash into the car.
The command section:
In this section is the major I/O processing stuff. Here you can find the CPU which is programmed to communicate with the motor controlling unit, sensors on the gate, with the remote control unit etc.
This little IC is nothing else then several darlington transistors put together into one small IC.
This is an ULN2003A type of darlington array with seven NPN darlington pairs.
I use this IC very frequently in my project where I wish to protect the output pins from my CPU or I need a bigger load to supply with juice than CPU output can handle.
This ULN2003A is used in this case to control the relays. The ULN2003A get a power on signal from the CPU on some pin and then the needed relay will start to working. If this part is bad then the relays won’t work.
This eeprom is used to store some calibration parameters of the gate. Something like of how many signals should be got from the rotary encoder from the motor to full or half open or close the door, there are the codes for the remote control unit stored too etc…
If this part or the content of this IC would be defect then I assume the door would not open/close or the remote control unit wont response etc…
This section is for communicating with the remote control unit. It is constructed on the TDA5200 single conversion receiver for receive frequencies bands 868-870 MHz and 433-435 MHz. If this goes bad you probably won’t have the ability to control your gate with your remote control unit.
As the technician told me the two relays were not working I focused on the relays and the ULN2003A ic. After I checked the relays and the protecting diodes which I could not capture because they are under the relays and hard to see them I moved to change the ULN2003A.
I called the technician guy and give him the pcb because I could not check all the operations in my service and told him to give me a feed back. After around 30 min I got a call the mobo is working and the gate is moving again as it should.
Conclusion, always check first if the power section is delivering to the unit, then the I/O section and then go to the parts which are between the control section and I/O section.
In most of case in my career I found the problem in the connection section between the I/O section and the control section. The connection section is that area where it comes to connection between the CPU and the relays in my case above. It could be a step motor driver or a classic DC motor connected on the CPU, there is a connection section too, maybe one heavy transistor or a complex driver unit.
Some friends of mine wasted their time searching for parts around the CPU, the relays, in the power section etc. but the main problem is between the cpu and the I/O board parts.
Sometime customers bring to me their equipment with a “known failure” as somebody checked and told the CPU is bad. To kill the CPU is not a big deal but it is hard if the electronic circuit is designed on a proper way. All I/O pins are protected on the CPU outside and the CPU inside too.
So, it is possible to burn the CPU but hard to do. After this repair, I got another several board for repair with similar problem. All of them had a ULN2003A problem. Why? I never figured out…
I hope you enjoy this tutorial and will save lot of repair time.
This article was prepared for you by Christian Robert Adzic from Novi Knezevac-Serbia.
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