Ok, the solenoids i am operatign with are the 24VAC, so looking for better transformer for PCB

 

Ok, the solenoids i am operatign with are the 24VAC, so looking for better transformer for PCB

Why use solenoids that require continuous power while valves are far less demanding on power?

 

Its a one requirment for the site, its going to be used? What valve do you use

 

The valve was already in an irrigation timer that had a programmed watering schedule.
I programmed my own microcontroller to include some additional intelligence with regards to rainfall and soil moisture.

Is your application for drip irrigation or water sprinkler? Not that it matters but sometimes the hose water pressure can make a difference.

 

I just arrived and read this thread.
NOW it seems that there is new information.
The TS owes the participants so far a lot more information as to the requirements and the resources.

 

Ok, it seems it would be much simpler to keep the DC and AC separate, as my DC current requirements could mean a larger transformer ,which could be unessary.

I am testing the following 24VAC transformer:
162G24
Low Voltage PCB Mount - Low Profile - 1.1 VA to 36 VA (162-164 Series) - Hammond Mfg.






Pins3 and 2, and pin 7 and 6. are they shorted?

 

Hello,

No, the connections 2,3 and 6,7 are open.
They can be used to put the coils in series or parallel.
Have a look at this drawing from ILP:


Bertus

 

So if we need to make 240V to 24V, what must we connect to the particular transformer?

I think I need to set it to Series mode.

 

This is what i have done on my PCB. Should i remove the shorts or would it still be ok? It seems like there are bing shorted in the transformer

 

Hello,

The transformer is a 2 x 12 volts output.
If you want to go from 240 to 24 volts, both sides must be in series.

Bertus

 

So what I have done on the PCB layout is that correct?

 

Hello,

Yes, both sides are connected in series.

Bertus

 

Great, but are they already connected internally as well or is it a externally connection that normally needs to be done?

 

Hello,

They are not connected internaly.
If there was a connection, the series/parallel connections would not be possible.

Bertus

 

I would not make the PCB symmetrical like that, too easy to flip it and connect it backwards. No need for all the vias and fat traces- on the primary-side even 1A is seen (clearing the fuse, so the PCB traces are not the fuse).
The fuse rating should be on the silkscreen and in North America 300% fusing is OK for small transformers.
That gives for 240VAC 0.15A max. and around 83-100mA (for 120VAC 0.3A max. and around 0.167-0.2A) for the ball park fuse size.

Also note small VA power transformers have quite poor regulation, their output voltage goes high at light loads.
I see about 35% (Tamura 3FL24) giving close around 32VAC out at no load, for 44VDC at the bridge rectifier.
Your buck-converter needs to be able to take this.

 

The PCB has been sent for manufacturing as part of a prototype batch, so I can make changes in the next PCB run.

Originally, I was aiming to have a single transformer that would also contribute to the DC voltage, but I now plan to keep both transformers independent.

I have added a fuse on the 24 VAC side.