jbarchuk:
yashiharu:
so, i should go for the following environment set for future?
AC <---> PSU( 3-15v 10A) <---> 8 channel relay <---> UNO(usb powered)
then i can play almost whatever i want in SAFE?I've seen those 8ch relay boards they look very nice.
However if you have the potential to go that far you need more PSU to carry it, -or- PAY RAPT ATTENTION to the limits.
2A capacity per relay
x8 = 16A
x50% safety margin = 24AYou don't need 24A unless you intend to go that far, with all loads on at the same time.
A 10A PSU never run at more than let's say 80% 8A means you can never turn on more than 4 relays @2A each at the same time.
If you don't need them to all be on at once, and you pay careful attention i software to NEVER turn on more than 4 at once, then you're fine.
In addition to a fuse on each pump I'd also add a fuse to the power output of the PSU, because if the software fails to keep the load down, the PSU will make it's best effort to deliver what it's asked for. If it's not fused or circuit breakered to protect itself then something will eventually overload and burn out (or catch fire.)
I'm not entirely sure of the -timing- aspects of this kind of power management, through relays, with inductive load. Relays take 'x' amount of time to disconnect power, (coil de-energises and magnet pulls contact open.) The speed of one relay disconnecting while another relay makes connection might have an -overlap-, that causes a brief but definitely measurable overdraw on the PS. Inductive loads typically draw a lot more power during startup, which if there is an overlap time would be in that time span. It might be insignificantly brief, or over time it might be significant to the lifespan of the PSU. Only an Engineer can read the specs the right way to determine what other margins might be needed to be built into the timing. Or an Engineer would specify what higher capacity PSU is required to allow for such overlaps and startup power surges.
very very good info $)
i got what you mean. thx
omg! program fail might happen ...
may i know which kind of PSU you recommended with fuse?