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Author Topic: C10 BOB use with 12VDC Relay  (Read 2338 times)

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C10 BOB use with 12VDC Relay
« on: December 24, 2016, 03:34:30 PM »
How do I wire a 12VDC relay with the C10 BOB. I'm using a 12VDC relay for my coolant because it's DIN rail mounted. Is there a way to do this?
Re: C10 BOB use with 12VDC Relay
« Reply #1 on: December 24, 2016, 04:47:05 PM »
Hi,
not directly, the TTL buffer chip inside the BOB is STRICTLY limited to 5V.

A couple of ways to achieve it:
1) use a little 5V relay and use its contacts to turn on the 12V one,
2) use an NPN transistor or Mosfet as the 12V switch which can be turned on by the BOB output, requires one resistor, one transistor and one diode.

Either way you will still require a 12V power supply to energise the relay coil.

Craig
My wife left with my best friend...
     and I miss him!
Re: C10 BOB use with 12VDC Relay
« Reply #2 on: December 24, 2016, 06:40:31 PM »
Hmmm ok. Kind of thought so. Thanks. I already have 12V in there for the VFD so that's not a problem. Probably easier to find a DIN Rail relay that operates on 5V.
Re: C10 BOB use with 12VDC Relay
« Reply #3 on: December 25, 2016, 01:37:03 AM »
Hi,
maybe easier said than done. Remember that the BOB is limited to about 20mA, and if you're being conservative you would try
to limit it to less than 10mA. It likely to be a pretty small relay and therefore risk overloading its contacts with any reasonable load.
Further the majority of relays for industrial purposes are 24V so you may have a limited selection.

At work we buy cheap components by the hundred, or at least I do while the boss complains and whinges!
BC547 60V 100mA NPN=7cents,
4.7kOhm 125mW resistor=1.8 cents
1N4148 75V 50mA diode=2.2 cents

You can see where I'm going with this....

Craig
My wife left with my best friend...
     and I miss him!
Re: C10 BOB use with 12VDC Relay
« Reply #4 on: December 25, 2016, 11:53:24 AM »
True. Thanks.
Re: C10 BOB use with 12VDC Relay
« Reply #5 on: December 25, 2016, 12:10:42 PM »
Hi,
just as a matter of interest what are you trying to control with the relay? I know you said 'coolant' but it it AC or DC
and what voltage?

You may have seen 'solid state relays' advertised, they take a modest DC input signal and can switch very substantial
loads, typically AC but in some cases DC as well. Mostly they are optisolated, ie any fault or rubbish happening on the
load side will not propagate back to your BOB/controller. I think $10-20 should get you an example capable of switching
and coolant pump I can imagine.

Craig
My wife left with my best friend...
     and I miss him!
Re: C10 BOB use with 12VDC Relay
« Reply #6 on: December 26, 2016, 12:31:24 AM »
Yes I'm thinking of using a Solid State Relay.

Its just a 120VAC aquarium pump, but that's for my mill as I'm rewiring it in a new cabinet. Before I had it hooked up when the VFD turned on and I didn't like doing it that way.

I will need some SS relays for my Mori SL1 that I'm retrofitting. It has a real sump coolant pump 220VAC, not sure how many amps though.
Re: C10 BOB use with 12VDC Relay
« Reply #7 on: December 26, 2016, 02:00:39 AM »
Hi,
I looking on the element14 website, my goto place for things electronic and may have lead you astray, good ones
capable of a decent load are more like $50.

I did see some DIN rail types, had a fairly modest load though, 100mA at 48V, my guess is that they are designed
to switch contactors on and off.

There are too the 'brick' type with 4 screw terminals, have used a few of that type at work, capable of 3A at 240VAC, may
be of interest to you for your coolant pump, not DIN rail that I saw.

I repair welding equipment for a living and I've seen LOTS of inverter type machines go bad. As a VFD is an inverter of a type
they can likewise make a big mess. I would not power one through a solid state relay no matter how good. BOB to solid state relay
to 'kick anus' contactor yes---solid state relay only between VFD and BOB/ESS/PC no. I mean the AC input side to the VFD here
the VFD inputs don't concern me that much.

Rather depends on how permanent you want your solution, as they  say 'there is nothing so permanent as a temporary solution'.

Craig
My wife left with my best friend...
     and I miss him!
Re: C10 BOB use with 12VDC Relay
« Reply #8 on: December 26, 2016, 02:40:52 AM »
That's not what I meant. The VFD is controlled by a C6 board which is it's function. When I'm switching a motor on, I use motor contactors; I mean when it's a heavy load motor.

For my mill it's just a simple aquarium pump at 120VAC.

For my lathe it'll be motor contactors for the coolant pump, spindle coolant/oiler, hydraulic pump and auto oiler.

I use automation direct for most of my electronics that deal with automation. SS Relay DIN mounted is $20.
Re: C10 BOB use with 12VDC Relay
« Reply #9 on: December 26, 2016, 05:31:37 AM »
Hi,
that's good news, be a shame to see a VFD take everything out.

Those SS relays sound like pretty good buying.  New Zealand is a pretty small market and sometimes we end paying
thru the nose for things. The international suppliers like Element14, DigiKey and the likes are usually  good pricewise
but on some lines, and looks like SS relays in this instance, not so good.

At $20 I could build up a opto-triac device or better an opto-dual anti-parallel SCR setup but a lot of shagging around
to save a few bucks. At $50 I would consider it.

Craig
My wife left with my best friend...
     and I miss him!