DC or AC Voltage reduction and relay help

[aspecthc]

Hi,

I hope someone can help me, I am a a new to this.

I am trying to get some window blinds (electric) to work on a Control4 system, These are not your typical blinds. They are 240v AC and go through a relay with a lower voltage coil.

My problem is I can't tell if the coil voltage is AC or DC. I would assume it is DC as I would not think the switching mechanism would work if it were AC

I have some pictures of the meter I used to check. (three in total). Any help would be good with that one.

Second problem,

The blinds currently work on a rocker style switch with a common Live (we will know the voltage if I get help on the above). Push the switch up and the blinds will go up and push the switch down to make them come down. My idea is to wire to coil of the blinds relay to the Control4 relays Common to Com and the Negative to NC and share the common to the reverse.

The Control4 Relay is rated to 36V AC 2amp or 24VDC 1amp, I am struggling on how to make the connection between the blind and the Control4 system

Thank you in advance

 

[Arouse1973]

Hello
Where are you measuring the voltage, can you show us a picture of that? You are also measuring current, where are you measuring that also? If you use the NC terminal of the control relay then when the control gear is not powering the relay the blinds will go up, is this correct? I guess the limit switch stop them in one position until you reverse the power with the relay.
Adam

 

[aspecthc]

Hi Adam,

I was measuring the voltage and current off the input or coil side of the relay on the blinds. I can send a picture tomorrow morning.

Basically I was holding the probe from the tester on the live and the other probe on the negative.

My problem is that the blinds relay is working on a higher voltage that the Control4 (home automation processor) relays are rated to. I need to somehow lower the voltage to below 24V so I do not damage the home automation processor

Currently to make the blind go up or down you just need to short the live with either of the negative (one for up and one for down)

Thanks
Simon

 

[Arouse1973]

Hi Simon I am confused as to why you have a D.C and A.C measurement.
Adam

 

[Arouse1973]

What Control4 system do you have? Can you link to the device?
Adam

 

[aspecthc]

Hi Adam,

So am I. I got a reading on both, I think its a DC reading but I would be interested to know how I can find out once and for all.

Can you have a relay with a AC coil voltage?

 

[aspecthc]

https://dealer.control4.com/Images/Downloads/C4-HC800-BL-1/RevD_HC-800_InstallGuide.pdf

Simon

 

[Arouse1973]

Hi Adam,

So am I. I got a reading on both, I think its a DC reading but I would be interested to know how I can find out once and for all.

Can you have a relay with a AC coil voltage?

Yes you can get A.C relays. Does the relay have any markings on it to give a clue, maybe we can Google it.

 

[aspecthc]

It has nothing, its just a clear box about the 30mm x 30mm

Is there anything I should be looking for?

 

[Arouse1973]

AC relays have a shader ring on the top of the coil it might look like a square piece of metal with a hole in it. Can you see anything on the side of the relay? What about the model of blind controller, do you have any details for that?
Adam

 

[aspecthc]

I will have to look tomorrow as the blinds are in the office. I will post picture of what is installed and how I was testing the voltage and current

Simon

 

[Arouse1973]

Ah I just thought it is most probably DC. The meter is not a true RMS meter so it might be assuming there is a -30V portion also and computing that as twice the voltage which is why you get 60 Volts or so. Sorry should have noticed that before.
Adam

 

[aspecthc]

Hi Adam

http://www.necogroup.eu/uploads/1/5/6/3/15633066/neco-product-brochure.pdf

Just found this, the blind controller is the GC4 contactor on page 26

Simon

 

[aspecthc]

Hi Adam,

If we assume its a DC voltage how do I get it below 24V so I don't damage the Control4 controller?

Simon

 

[Arouse1973]

If the blind winder coils is rated at 24 Volts and the control gear can only switch say 18 Volts then you can't connect them. Now this voltage is rated at 2 Amps and I would be surprised if the blind control relay would draw that much current. So its telling you the power rating of the contacts. So for the slight difference in voltage I would have thought you would be ok although you do have to consider the inrush current of the other coil. It's not like you are going to get huge sparks on the contacts from such a low voltage. You could however use a transistor which is controlled from the controller which switches the blind relay.
Adam

 

[aspecthc]

I think I understand.

You dont think the 6V difference will course a issue?

If I did want to drop the voltage I should use a transistor. Can you point me to one or where to buy one please

Simon

 

[Arouse1973]

I don't think so as long as the contacts power rating in this instant is higher that the volts x current you are switching.
Adam

 

[Arouse1973]

Oh one other thing I thought I would just mention, but the blind unit probably has one. Is a flyback voltage protection diode across the coil. I noticed that the control4 says it can drive blinds so they may have thought of that also.
Adam

 

[hevans1944]

... I got a reading on both, I think its a DC reading but I would be interested to know how I can find out once and for all.

This multimeter has a polarity indication (-) if the red test lead is negative with respect to the black test lead. Swap the test leads while measuring DC volts and if you see the minus sign appear in the display, that is a good indication that what you are measuring is actually DC and not AC.

Many of these inexpensive meters do not employ a DC blocking capacitor when measuring AC, so they will happily provide you with an "AC" reading when DC is applied and the meter is set to measure AC volts.

Another way to verify that DC is what you are measuring is to charge up a 1 μF low-leakage film capacitor by briefly connecting it across your voltage source. Then quickly use the multimeter on its DC function to measure the voltage across the now-disconnected capacitor. Do this several times and record the results. An AC voltage applied to the capacitor will result in random readings when the capacitor is disconnected and its voltage measured. A DC voltage will provide consistent, same polarity, readings that decay as the multimeter discharges the capacitor.

 

[Arouse1973]

Found a cheap DVM supplied by one of my suppliers. Looks just like yours. I found that if you put a DC voltage onto the probes when the meter is set to AC. You get twice the voltage. Opened it up and well quite complex, it consists of 1 diode, 1 capacitor and about 6 resistors and a black blob.
Adam