Preface... I believe I am above average at troubleshooting stuff, and this one has got the better of me.
Ok, a simple consumer gadget using a microcontroller to switch an outlet on and off at programmed times, a glorified lamp timer...
Interface is a small LCD screen with 4 front panel buttons for setting clock and program on/off times, A top on/off override button and a top slide switch to select between off auto mode, and a random auto mode that is +/- 15 minutes of programmed times.
Almost everything works.
The clock works and keeps reasonable time, The manual on/off switch switches the relay on/off, and with the front buttons I can program in 6 sets of on/off events.
But what doesn't work, is in either of the two active mode switch positions, no programmed on/off...
So I opened it up... kind of surprising how much stuff I found inside considering I bought this for <$13.00 at Walmart.
The power board was cheap single sided bakelite with through hole parts. A relay and even a back up battery, so it doesn't get stupid every time the power blinks off.. then there is another SS board for the front buttons, the processor sits on a small 4 layer SMD PCB but the processor is direct bonded to the PCB under a lump of epoxy.. but I can probe the pins that fan out to relatively large by comparison 44 pin square SMD package where a normal micro would fit.
Since everything works but the modes, the mode switch is the obvious candidate to check. It's a single pole triple throw, with the wiper tied to ground, and selectively shorting one throw at a time... I trace these three switch throws to three consecutive input lines on the micro controller. As expected the grounded pin is at 0V and the other two are sitting up at 2.5V the PS voltage for this puppy. In each position of the mode switch only one of the three lines is held low and the other two at logic high.
So as far as I can confirm the controller is running fine..the clock sets and keeps good time, it also accepts and displays 6 sets of program times. The manual button works, which also confirms that the micro controller is able to talk to the relay switching the outlet power on and off when it wants to.
So my list of possible faults is pretty slender.. Since I don't see any pull up resistors, I am ASSuming that the logic pull ups are built inside the micro controller, which confirms also that the switch logic is making good connection to the controller.
Short list also very unlikely is faulty program code inside controller, or damaged input ports on the controller. Actually two input ports need to be damaged since it has two different on modes and neither works.
When I asked the company who made these what they through the problem was they answered, me opening it up.
At least they have a sense of humor.... I told them if it worked I wouldn't be opening it up.... 8)
OK, I'm open for suggestions, I am truly stumped on this one... It's simple, everything looks like it should work and most is, but it doesn't do the one thing it is supposed to do.
JR
Ok, a simple consumer gadget using a microcontroller to switch an outlet on and off at programmed times, a glorified lamp timer...
Interface is a small LCD screen with 4 front panel buttons for setting clock and program on/off times, A top on/off override button and a top slide switch to select between off auto mode, and a random auto mode that is +/- 15 minutes of programmed times.
Almost everything works.
The clock works and keeps reasonable time, The manual on/off switch switches the relay on/off, and with the front buttons I can program in 6 sets of on/off events.
But what doesn't work, is in either of the two active mode switch positions, no programmed on/off...
So I opened it up... kind of surprising how much stuff I found inside considering I bought this for <$13.00 at Walmart.
The power board was cheap single sided bakelite with through hole parts. A relay and even a back up battery, so it doesn't get stupid every time the power blinks off.. then there is another SS board for the front buttons, the processor sits on a small 4 layer SMD PCB but the processor is direct bonded to the PCB under a lump of epoxy.. but I can probe the pins that fan out to relatively large by comparison 44 pin square SMD package where a normal micro would fit.
Since everything works but the modes, the mode switch is the obvious candidate to check. It's a single pole triple throw, with the wiper tied to ground, and selectively shorting one throw at a time... I trace these three switch throws to three consecutive input lines on the micro controller. As expected the grounded pin is at 0V and the other two are sitting up at 2.5V the PS voltage for this puppy. In each position of the mode switch only one of the three lines is held low and the other two at logic high.
So as far as I can confirm the controller is running fine..the clock sets and keeps good time, it also accepts and displays 6 sets of program times. The manual button works, which also confirms that the micro controller is able to talk to the relay switching the outlet power on and off when it wants to.
So my list of possible faults is pretty slender.. Since I don't see any pull up resistors, I am ASSuming that the logic pull ups are built inside the micro controller, which confirms also that the switch logic is making good connection to the controller.
Short list also very unlikely is faulty program code inside controller, or damaged input ports on the controller. Actually two input ports need to be damaged since it has two different on modes and neither works.
When I asked the company who made these what they through the problem was they answered, me opening it up.
At least they have a sense of humor.... I told them if it worked I wouldn't be opening it up.... 8)
OK, I'm open for suggestions, I am truly stumped on this one... It's simple, everything looks like it should work and most is, but it doesn't do the one thing it is supposed to do.
JR