Go Down

Topic: PID, ground and fuse (Read 2361 times) previous topic - next topic

francescor

Hello,

I have a Omron  E5CSV-R1T-500 AC100-240 PID Temperature Controler. It has an integrated reley SPST-NO, 250 VAC, 3A (resistive load)
http://uk.rs-online.com/webdocs/1378/0900766b81378677.pdf

I would like to control a small heat mat (12V, 1.25W) and set the temperature to 30 C.

I have two questions:

1. how do I ground the power supply? I have seen connecting the wire just to a piece of metal. I do not want to do mistakes since my little knowledge of electronics. I would like to know in detail how to do it.

2. Do I need any fuse for my application?

Thank you very much for your help

Francesco




Paulcs

You install the Omron in a small box.  The incoming power cord should be 3 conductor.  (USA = hot, neutral, ground.  UK = hot, hot, ground).  The ground wire can connect inside the box to whatever product need a ground.  The Omron doesn't use a ground.  If the box is metal, ground that.  If the power supply source wants a ground, then ground it.

The power supply provides a 12V that might go into Omron terminal 1, comes out Omron terminal 2, goes through a fuse, goes to the mat, and mat return wire goes to the power supply.

The fuse protects the wiring.  So if you use 18AWG wire, anything such as a 1, 2, 3, amp fuse will be fine for your 0.1 amp load.

The incoming power cord should be plugged into an external outlet that has a fuse of circuit breaker.  However, it is recommended to put a small (1, 2, or 3 amp) fuse on the AC hot, before going into Omron terminal 9.

francescor

Hi Paulcs,

thank you for your answer. I have understood how to do the wiring and how to connect the fuses.

However, I would prefer to assemble everything on a wodden table first, because I do not have the tools to cut the metal box at the moment. How do I ground in this case?

Is it possible to use a power cord  with just two conductor or is that dangerous? If I can go for it, I would do just the wiring as you described.

Thank you again,
Francesco

tinman13kup

From what I see, this is just an ON/OFF relay based on a thermocouple. The unit is isolated from what you are trying to control.

What that means is you have to get mains power to pin 9/10 (no ground terminal). You also need to put a thermocouple for your pad to pins 4/5, and using a separate 12V power supply, the (+) would go to pin 1, and pin 2 would go the (+) of your mat, while the (-) from the mat would go to the 12V supply.

The thing to be careful of is the exposed mains connections on the rear of the unit. Care must be taken to avoid any possible contact with them. If it is a standalone project, using a plastic box would be just fine, and you wouldn't need the ground on the mains. Use metal and I would suggest using ground from the mains to the metal box.

I would not hesitate to set this up on a table for testing , provided you are mindful of those mains connections
Tom
It's not a hobby if you're not having fun doing it. Step back and breathe

francescor

I will take care that there will no any contact between the wires on the rear of the unit.

The final setup will be in a grounded metal box and I will use fuses too. I want to be sure everything works before start to cut into the metal.

It is not clear what can I use as 12V additional power supply. Can you post any example of such unit?


tinman13kup

I will take care that there will no any contact between the wires on the rear of the unit.

The final setup will be in a grounded metal box and I will use fuses too. I want to be sure everything works before start to cut into the metal.

It is not clear what can I use as 12V additional power supply. Can you post any example of such unit?


That depends on your heater. Is it 1.25W or 125W? If it's 1(.)25W @12V, you need a 12VDC supply with a current capacity >= 200mA. If that is 125W, then you need around 20A supply. A heat pad of 1W really isn't very big, while 125W can get pretty hot. Big difference between them.

If you have any old electronics power supplies laying around, look on the case. It will tell you the voltage and current it can put out if it is 1(.)25W. If it is 125W, you might be able to use a atx power supply from a computer. You can also use a car battery temporarily, but it won't last real long. You can also get a dedicated 12v benchtop powersupply with the current capabilities you need for $15/20US.

 What is this project for?
Tom
It's not a hobby if you're not having fun doing it. Step back and breathe

francescor

the heater is very small: Silicon Heater Mat, 1.25 W, 25 x 50mm, 12 V dc.

I need to build a small incubator that goes up to 30 C, it must heat around +8 C compared to room temperature. The heater will be placed in a polystyrene box.

If not enough powerful, I might add a recepticle and use a heating cable. I think that 15W should be enough.

I have a universal power supply that goes up to 12V, I might also check for other charger. Shell I just cut the wires and connect them as you described?

What about the A of the internal Relay? Are 3A just enough for my application?

tinman13kup

the heater is very small: Silicon Heater Mat, 1.25 W, 25 x 50mm, 12 V dc.

I need to build a small incubator that goes up to 30 C, it must heat around +8 C compared to room temperature. The heater will be placed in a polystyrene box.

If not enough powerful, I might add a recepticle and use a heating cable. I think that 15W should be enough.

I have a universal power supply that goes up to 12V, I might also check for other charger. Shell I just cut the wires and connect them as you described?

What about the A of the internal Relay? Are 3A just enough for my application?
Yes, if your supply is rated 12Vdc @ a minimum of 200mA, it will work. You can cut the barrel plug off, separate the two wires and hook them up as I posted.

With the relay specs, it tells you how much power it CAN handle max. Just like the power supply, you can safely use under that amperage figure.

If you use the heating cable, you can do a very similar setup. You would cut one of the wires from the plug (2 wire plug) and connect those ends to pins 1/2 and plug it in and your controller would keep the temp via the thermocouple.

Either way, just make sure and protect the back of the controller unit because of the open mains terminals. Should you forget and just grab the unit, you don't want it to grab you back. You can use some thick plastic sheet and tape it on if you wanted.
Tom
It's not a hobby if you're not having fun doing it. Step back and breathe

francescor

Thank you very much.

Just one last detail. How do I understand what is  +or -? On the heating mat there are only two white cables that look the same. The power supply has two blak cables, one has a white line on it.

Thank you again

tinman13kup

The heat mat might not be polarity sensitive (it doesn't matter how it's hooked up). As for the power supply wires, I have actually seen it both ways. Easiest way is to separate them, plug the thing in and use a voltmeter. If the readings say 12v, the wire with the red voltmeter probe on it is +. If it says -12v, the one with the black probe is +.

In general, it doesn't matter if you are switching the + or the - with the relay. It will operate the same way. In practice however, it is always wise to switch the power if you can. What that does is makes the heat mat and all the wires to the mat at -. With dc, that generally means ground. With 110vAC, that means neutral (which is still gnd), but with 220VAC, it doesn't matter. The pad would always be "hot" whether the relay were closed or open.

For what you are doing, just 12v @ mA current, just cut one wire and connect the 2 ends to pins 1/2 of the controller and don't worry about it.

 What is your mains power? 110 or 220VAC?
Tom
It's not a hobby if you're not having fun doing it. Step back and breathe

francescor


francescor

Where do you suggest to add the fuses? Main and the 12 volt too?

tinman13kup

Where do you suggest to add the fuses? Main and the 12 volt too?
That's the beauty of it. The controller is already fused, and your power supply is as well. If your 12V supply puts out 10A, then you might consider an inline fuse (1A) on the + wire before the relay. If your 12v supply only puts out 200mA, I wouldn't worry. Just use good wiring connections. No taping wires together, no bare wires laying about, no twisting connections together.

Before you cut the wire on the 12v supply, make sure you leave enough wire on the plug side to get to an outlet, and enough on the other end to reach your heat pad.

At 1W, I would make sure and put this in an insulated box that is only big enough to accomodate what you are incubating. Use a lid. Give it time to warm up. Don't forget to stick the thermocouple in the box.
Tom
It's not a hobby if you're not having fun doing it. Step back and breathe

francescor

Thank you again. The power supply goes up to 1A. My Messor capitatus ant queens thank you as well. I let you know how it goes.

tinman13kup

Thank you again. The power supply goes up to 1A. My Messor capitatus ant queens thank you as well. I let you know how it goes.
If you are trying to heat any mass or volume with that, it may not ever turn off. Just watch it over a day or two and see. You could safely add a second identical unit by attaching it just like the first to the same power supply.
Tom
It's not a hobby if you're not having fun doing it. Step back and breathe

Go Up