On Friday, August 4, 2017 at 10:02:53 AM UTC-5, wrote:
On Fri, 4 Aug 2017 05:27:19 -0700 (PDT), Uncle Monster
wrote:
On Thursday, August 3, 2017 at 7:19:43 PM UTC-5, Dean Hoffman wrote:
On 8/3/17 3:38 AM, Uncle Monster wrote:
On Wednesday, August 2, 2017 at 8:53:22 PM UTC-5, Dean Hoffman
wrote:
Can a solid state relay switch other solid state relays?
Anything to watch other than to wire them up? I didn't spend a
lot of time looking but didn't see an answer to this question.
The solid state relays seemed like an answer to a problem I had to
solve. The switching ssr needs to operate two others. One is a
quarter mile away, the second is a half mile away.
Thanks, Gentlemen
Who are you calling Gentlemen? I don't see why the solid state relay
couldn't switch on other solid state relays. What type of relays are
you considering for your project? What voltages and current will you
be switching? AC or DC voltages? You might also consider putting
lightning protection on your control cable. Another thing you may
consider would be wireless control signals to cover the distance. I
did a lot of control system work and solid state relays are a mature
technology with many choices as to what voltages and current the
relays will handle plus what voltages AC or DC will trigger them. ?
(?)?
[8~{} Uncle Triggered Monster
I need/want to stay under 30 volts for the control voltage. The
code will let us do that without grounding and interlocks on the panels
where the controlled relays are mounted. The reason for the DC is
those seem to be much more common.
Plan A was a master ssr at the center point of an irrigation system.
It would be activated by 12vdc from an irrigation engine located in
the northeast corner of a field. Eighteen hundred feet away give or
take. The masters output would be supplied by 24vdc. The load was
to have been the two slave solid state relays. The first slave
would've been in a well panel straight north of the master about
thirteen hundred feet away. The second slave would've been in a well
panel about thirteen hundred feet west of the first slave.
The slaves would've been switching power to a 480vac three phase
motor starter. They'd have had about 240vac through them.
The supply house sent zero point switching ssrs. Control voltage
is 4-32vdc.
Output 600 vac. I think that might have been a problem with the 3
phase. They didn't work every time, either off or on. I solved that
perceived problem with a 480x120 transformer. The slave ssrs are now
switching single phase 120 going to a mechanical relay. That relay runs
the pump starter.
The problem now is the slaves won't obey the master. My guess was
they don't impose enough of a load on the master. I must be on the
right track judging from the other responses.
Someone else buried the pipe and wire long ago. The wire is 12 uf
with ground. Our customer asked us to make the irrigation system kill
the wells and any failure kill the other three parts of the group.
Three wells are supplying water to one center pivot at a time.
I'm used to mechanical relays, switches, and contactors. Those won't
work due to the voltage drop.
Any ideas?
There are solid state relays that have a wide voltage range to trigger them. The thing I'd be most worried about is what would happen to your control system when there is a nearby lightning strike. If you're running a very long control cable to low voltage triggered solid state relays, the induced voltage surge on the control cable could burn out your relays. If there is electrical power at your remote pumps, consider wireless control. ?(?)?
http://www.remotecontroltech.com/
[8~{} Uncle Uncontrollable Monster
I think the lightning problem can be mitigated with some big MOVs
kicking off at 30v or so. Since SSRs are, by there nature, isolation
devices you do not have a direct path. I would also loop the leads
through some big ferrites but other than that it is not a big worry.
Lightning surges are generally common mode transients.
SSRs are cheap and pretty tough. Just keep spares and worry about the
lightning problem when you see it is a problem.
If I was doing the control lines I'd use what I used to protect telecom lines but there are protectors made for low voltage control cables but I still think a wireless solution should be considered. ヽ(ヅ)ノ
http://www.l-com.com/surge-protector...rge-protectors
[8~{} Uncle Surging Monster