RE: Relay light control problem

["'Simon Coates' simon@xxxxxxxxxxxxxxxxx [ukha_d]" <ukha_d@xxxxxxxxxxxxxxx>]

Simon,

=20

70W fluorescent draws approx. 85W of inductive load.

As a rule of thumb you should multiply this by 10 for initial current draw
=
(more for switch off spike)

So for two lamps that=E2=80=99s over 7 amps, and the 5 amp rating on the
re=
lays is for a purely resistive load.

They=E2=80=99re over their current limit, that=E2=80=99s why they work for
=
a while and then eventually start to weld together.

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HTH,

=20

Simon

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=20

From: ukha_d@xxxxxxx [mailto:ukha_d@xxxxxxx]=20
Sent: 13 February 2017 12:28
To: UK Home Automation List <ukha_d@xxxxxxx>
Subject: Re: [ukha_d] Relay light control problem

=20

=20=20

Hi Dave,=20

=20

the relays are rated at 5A  for 220V.

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The lights being controlled have two 70W tubes

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=20




Regards

Simon

---

"sorrowful, yet always rejoicing; poor, yet making many rich; having
nothin=
g, and yet possessing everything" 2 Cor 6:10

=20

On 13 February 2017 at 08:36, 'Dave McLaughlin' dave@xxxxxxx=
<mailto:dave@xxxxxxx>  [ukha_d]
<ukha_d@xxxxxxx <ma=
ilto:ukha_d@xxxxxxx> > wrote:

=20

Hi Simon,

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What is the rating of the relay at 220Vac?

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What is the power of the lights themselves?

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It is possible that the relay rating is too low.

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Fluorescent lamps appear as an inductive load to the relay due to the
balla=
st so there is a higher inrush current.

=20

An option is to fit a snubber across the relay contacts.

=20

Dave=E2=80=A6

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Very funny Scotty, now beam down my clothes=E2=80=A6

---

=20

From: ukha_d@xxxxxxx <mailto:ukha_d@xxxxxxx>  [mailto:ukha_=
d@xxxxxxx <mailto:ukha_d@xxxxxxx> ]=20
Sent: 13 February 2017 15:14
To: UK Home Automation List
Subject: [ukha_d] Relay light control problem

=20

=20=20

Hi=20

=20

I've recently been trying to use relays to control the internal lights in
m=
y garage, but I've been having issues. They are fluorescent tubes, two
cont=
rolled by each relay. The relays are those ones you see all over eBay,
with=
GPIO level inputs for control by a Raspberry Pi etc.

=20

The issue I've had is that after a while they simply stick, always on. So
w=
hen the pi sends the signal for them to go off, the lights stay on.

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I initially thought it was a faulty relay, but I ordered a replacement and
=
fitted them on Saturday, and now one side is stuck again.

=20

Is it something to do with the load of these fluorescent tubes? Any ideas?




Regards

Simon

---

=20

=20





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Posted by: "Simon Coates" <simon@xxxxxxx>
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