OpenSprinkler Forums Hardware Questions DIY Kit Assembly Questions Troubleshooting lower voltage on 1 station

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  • #22327

    dman
    Participant

    Hi Ray, I have noticed that the voltage on station 2 of my v1.0 board is lower when activated than any of the other stations. For example it will read 20.5VAc when on, but all the other stations read 24Vac. I have reflowed the triac solder and looked at the board and all connections look good. Any thoughts on what I should be looking at to try sort this out.

    #23233

    Ray
    Keymaster

    There are several possibilities, but I think most likely it’s caused by an unreliable solder joint. I know you’ve checked the triac, but you should also check the joints on the resistor array and the 74HC595 shift register. A lower voltage probably means the triac is not turned on fully. This could be because the connection from the resistor or the shift register pin is loose. So check those solder joints and see if anything changes.

    #23234

    Gyro
    Blocked

    Hi Ray,
    I have built the open sprinkler v1.4u and I did have a bit of trouble with the unit starting a watering zone then after about 15 seconds, the unit would re-boot and start from scratch, I found that because I have a relay (taking about 20mA at 24v) and it operated 4 master solenoids (most would only have one) and then a zone (2-8) would operate the particular watering zone solenoid, (each solenoid drags about 130ma ac at 24v) so the over all current would cause the PTC fuse (thermister WH60 075)) to heat and go high resistant as its suppose to do and therefore at approx 17v AC being supplied (at the point after the PTC) then would reboot the unit, all stations would be switch off and it all recovered, so what I did for a fix was to put a 1amp fuse instead, I know that if a S/C was to happen, the triac would get red in the face and probably be destroid (which I think are good for 600-800mA), but could be food for thought, I may get a lower rated one and put in each triac Cct,
    cheers
    Gazza

    #23235

    Ray
    Keymaster

    @Gyro: you are right, the fuse is rated at 750mA, so having 4-5 solenoid running at the same time is likely to trigger it. The triacs are rated at 800mA continuous current and 8A impulse current. To be honest, when I designed the circuit, I didn’t realize that the PTC fuse is a slow-action type. So by the time it triggers, the triac may already be destroyed (say, if a solenoid is defective and short circuited). Therefore the PTC fuse may not be very useful.

    #23236

    Anonymous
    Inactive

    Opensprinkler v1.4u.

    The PTC fuse next to the power switch gets very hot. A station will run for about 10 to 15 minutes then the unit faults, usually with the LCD dimmed. Unplugging then powering returns the unit to previous operation.

    Power Supply output- 24VAC, 750mA
    VIN-GND 5V, Over range Ohms
    VCC-GND 3.3V, Over range Ohms
    Can cycle through stations- ~25V output, 0.18A on the active station.
    Rainbird Valve #35006905

    Seems like this load shouldn’t be a problem based on the previous posts. What should I check to trouble shoot?

    #23237

    Ray
    Keymaster

    I’ve seen issues with the PTC fuse false triggering, especially if the ambient temperature is high. I suggest that you solder a wire across the PTC fuse to bypass it.

    #23238

    Anonymous
    Inactive

    By-passed the PTC fuse. Seems to be working fine now. Will add a fuse block soon. May get a higher power supply so it may be a 2A quick blow fuse.

    Thanks again for helping.

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OpenSprinkler Forums Hardware Questions DIY Kit Assembly Questions Troubleshooting lower voltage on 1 station