April 29, 2015 at 10:41 pm #37231
I bought a OpenSprinkler to replace my 20yr old Toro controller (waiting for delivery). I’m hoping to use the Toro wall-wart / transformer but the instructions show using a 24VAC two-wire transformer. My transformer is this one. It has three wires/posts. One post on the transformer marked “0” (with black wire leading to a post on the controller marked “HOT POST”), one marked “15” (white wire leading to a post on the controller marked “15V”) and one marked “24” (red wire leading to a post on the controller marked “24V”). Should I be able to use this transformer on my yet-to-be-delivered OpenSprinkler device (leaving the “15” post unconnected I assume) or will it damage the OpenSprinkler device?
Your guidance is apprecieated.April 30, 2015 at 1:10 am #37243
The transformer you have will work fine with the open sprinkler. The link you provded shows that one output is 24Vac 22.5 VA .93 amp, which is perfect. If you use the “0” (black) wire, and the “24” (red) wire you will be all set. Make sure you disconnect, and/or insulate the “15” (white) wire so it does not accidentally touch anything it shouldn’t. It does not matter which order you wire the power connector to the opensprinkler, as it is AC.
Hope that is of some help.
BruceApril 30, 2015 at 12:56 pm #37255
I bought a OSPI with a Raspberry Pi 2
can I also use a 24V AC power supply which is higher than 500mA?
I choose a 2,0 Ampere (or higher) Power Supply can it destroy the OSPI?
KalleApril 30, 2015 at 7:01 pm #37264
Yes, 2.0A or higher is fine. The increased amperage allows you to open more stations simultaneously.April 30, 2015 at 7:08 pm #37265
Yes, a 2.0Amp 24VAC power supply will be ok. The OSPi and the RPi will together draw something around ~400mA (0.4A) under normal operation. The 24VAC input on the OSPi board has an inline fuse, which will blow if a fault…..such as a short circuit on an output, occurs. The OSPi will not draw more current from the power supply than it requires……just because your power supply is able to supply more current, it will not be used by the OSPi. The fuse will blow quickly, if a problem with the OSPi or RPi causes too much current to be drawn…..which protects both the OSPi and the power supply. There is also a secondary protection on the 5VDC output of OSPi, which is a polyfuse (see: http://en.wikipedia.org/wiki/Resettable_fuse for more details on how they work).
Hope That helps.
BruceApril 30, 2015 at 7:10 pm #37266
Samer is right. I feel like I need to write a blog post about this because it has been such a common question. Technically a power adapter rated at 2 amp means it’s capable of supplying 2 amp while still maintaining the rated voltage. But it’s not like the power adapter is constantly pumping out 2 amp — it just means that if your circuit draws 2 amp, it will still be able to guarantee the rated voltage. If the circuit draws more than 2 amp, the output voltage will start to drop and eventually collapse (which typically triggers a reset of the device). However, if your circuit only draws 1 amp, that’s totally fine, it’s not going to be destroyed or anything.May 2, 2015 at 2:57 am #37294
Okay, thanks a lot. Now, I bought a power supply with 830mA. That must be ok! 🙂
KalleMay 3, 2015 at 7:57 pm #37322
Fantastic. Thank you for the info. I’ll just disconnect the white wire from the (15) post on the toro transformer, electrical tape the post and wirenut and etape the white wire. Now if only the unit would get here. Not that I’m impatient or anything 😉
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