Repeater Delay Board
Here it is. This circuit is designed for those that have a repeater and need a delay between the receive radio and the controller. I use this on my 2 meter repeater. The purpose of this it to allow me to keep my repeater up and running without the need to have an input tone. I first started to think about this when the repeater would go through times that it would key up and down fast. After a while we figured out that there was another repeater no to far away with the same frequencies. Being that we were both coordinated correctly there was nothing we could do. After a wile it was found that the an amateur was just giving me enough power to key and then drop my repeater when he was talking on the other repeater. With this circuit it will prevent that. With this circuit it has a programmable delay between the time that the receiver gets the signal and when it is passed on to the controller. Now anytime that the signal is drop it resets. With this it will stop the sudden keying and dropping. I hope I have not confused anyone with this. If you have any question on this please contact me.
This project is a must for amateurs that have repeaters.
Parts and Circuit
The circuit:
(Click on image to view)
The parts list is fairly simple. Most all the parts can be obtained from your local electronics shop. The only parts that are a little more difficult is the three IC chips. I will give you more info on how to get those later.
It is very important that the power for Q1 be taken from the input side of U2. If you do not take the power before U2, Q3 and Q4 will not act correctly and Darlington pair will not allow Q1 to turn on and activate the pic chip. Also it is important that you use a 100pf capacitor to the base of the the Darlington pair. If you leave it out or install the incorrect capacitor it will not let the chip drop correctly and will cause it to keep kerchunking as we are trying to prevent.
The COR Ground signal from the receive radio is now much more sensitive since I added the Darlington pair to take care of a crashing problem that I was having. With this setup it takes a signal as great as 1 Mega Ohm to activate the delay timer. This fixed the problem that was found when the transmitter turned on it changed the resistance on the receive radio and did not have enough current going through to keep the repeater up and working.
| J1 | 1 | + Power, Connection Input |
| J2 | 1 | GND Power, Connection Input |
| J3 | 1 | COR + From Radio, Connection Input |
| J4 | 1 | COR - From Radio, Connection Input |
| C1 | 1 | .22 uF, Small Capacitor |
| C2 | 1 | .1uF,Small Capacitor, Optional |
| C3 | 1 | 100pf Capacitor |
| R1,R2,R3,R4,R5,R6,R8,R9 | 8 | 1K,Small Resistor |
| R7 | 1 | 1M,Small Resistor |
| D1 | 1 | 1n4181,Diode |
| D2, D3 | 2 | 1N4001 Diode |
| U1 | 1 | 16F628A, Microcontroller |
| U2 | 1 | 7805, Voltage Regulator Regulator |
| U3 | 1 | 2n7000, Mosfet |
| H1,H2 | 2 | Header |
| L1,L2 | 2 | Led, Any generic led will work |
| Q1,Q2 | 2 | Optocoupler, opt isolator |
| Q3, Q4 | 2 | 2N4403 Transistors PNP |
| O1 | 1 | Output +,Controller |
| O2 | 1 | Output GND, Controller |
| Socket 1 | 1 | 18 Pin Dip Socket for Pic Chip |
| Socket 2, Socket 3 | 1 | 4 Pin Dip Socket for Optocoupler |
The only parts that you may not find is the 16f628A pic microchip, and the optocoupler. Both can be purchased from Mouser. Later on this page I will give the code to program this chip with. If you do not have a way to program the chips please contact me and I can sell you a preprogrammed chip and send it in the mail to you.
The pic programming information.
The 16F628A is a programmable chip made by Microchip. This is the brains of the circuit. I have provided the hex file below that you can use to program your chip if you have the capabilities to do so. If you do not have the proper hardware and software, you can purchase the chip from me programmed.
Click here to download hex file.
Setup and Connections
Setting Up the Board
The board is easy to set up. There are only two things that need to be done on the board for it to work right.
First:
Power Connection. It is important that you connect the power correctly. This is a common sence item. I have included a protection device. This is D2 and D3. They are just to make sure that you can not damage anything on the board.
Second:
You need to set up the two jumpers to make the board understand the input signals. If you are using a Ground signal then you need to place both jumpers so that they connect pins 1 + 2 together. This allows voltage to go the the chip from the boards power supply and it will use the radios ground signal to turn on. If you are using a Positive signal then you need to place both jumpers so that they connect pins 2 + 3 together. This gives the chip a constant ground path and turns on when the radio sends + voltage to the controller.
Third:
Output. Use the correct output signal for your controller. This board will give you both a 5 volt signal and a ground signal. I have also included a diode to protect the pic chip on the + side.
Some Pictures of the finish board.
I am still building this page and will continue to add the reset of the information as I am able to.