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Optotriac resistor selection

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  Optotriac resistor selection bitrex <bitrex@de.lete.earthlink.net> - 2016-10-30 13:11 -0400
    Re: Optotriac resistor selection bitrex <bitrex@de.lete.earthlink.net> - 2016-10-30 13:13 -0400
      Re: Optotriac resistor selection Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2016-10-30 13:23 -0400
        Re: Optotriac resistor selection bitrex <bitrex@de.lete.earthlink.net> - 2016-10-30 13:35 -0400
          Re: Optotriac resistor selection Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2016-10-30 13:39 -0400
            Re: Optotriac resistor selection bitrex <bitrex@de.lete.earthlink.net> - 2016-10-30 13:45 -0400
            Re: Optotriac resistor selection John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-30 10:52 -0700
              Re: Optotriac resistor selection bitrex <bitrex@de.lete.earthlink.net> - 2016-11-01 12:29 -0400
                Re: Optotriac resistor selection Lasse Langwadt Christensen <langwadt@fonz.dk> - 2016-11-01 09:42 -0700
      Re: Optotriac resistor selection "Benderthe.evilrobot" <Benderthe.evilrobot@virginmedia.com> - 2016-10-30 21:39 +0000
      Re: Optotriac resistor selection Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> - 2016-10-31 02:50 +0100
        Re: Optotriac resistor selection "Benderthe.evilrobot" <Benderthe.evilrobot@virginmedia.com> - 2016-10-31 19:41 +0000
    Re: Optotriac resistor selection John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-30 10:28 -0700
      Re: Optotriac resistor selection bitrex <bitrex@de.lete.earthlink.net> - 2016-10-30 13:36 -0400
        Re: Optotriac resistor selection John Larkin <jjlarkin@highlandtechnology.com> - 2016-10-30 10:49 -0700
          Re: Optotriac resistor selection bitrex <bitrex@de.lete.earthlink.net> - 2016-10-30 13:54 -0400
            Re: Optotriac resistor selection Winfield Hill <hill@rowland.harvard.edu> - 2016-10-30 11:33 -0700
    Re: Optotriac resistor selection "Dave M" <dgminala@mediacombb.net> - 2016-10-30 12:47 -0500
    Re: Optotriac resistor selection Jasen Betts <jasen@xnet.co.nz> - 2016-10-31 05:30 +0000
    Re: Optotriac resistor selection piglet <erichpwagner@hotmail.com> - 2016-10-31 07:56 +0000
      Re: Optotriac resistor selection bitrex <bitrex@de.lete.earthlink.net> - 2016-10-31 05:36 -0400
    Re: Optotriac resistor selection Frnak McKenney <frnak@far.from.the.madding.crowd.com> - 2016-10-31 06:38 -0500
      Re: Optotriac resistor selection bitrex <bitrex@de.lete.earthlink.net> - 2016-10-31 08:59 -0400
        Re: Optotriac resistor selection Frnak McKenney <frnak@far.from.the.madding.crowd.com> - 2016-11-01 08:34 -0500

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#432990 — Optotriac resistor selection

I have a MOC3010 optotriac (from da junk box) that I'm trying to use to 
switch about 100VAC from a small inverter brick to a length of EL wire 
about a meter long.

Right now I'm driving the internal infrared LED through a 1k resistor 
from a 3.7 volt supply. The meter shows that the chip is drawing about 
3mA of current compared to when the pins are disconnected, so I'm 
assuming the LED is turning on, but it doesn't appear to be enough to 
fire the triac when it's hooked up to this load.

Can anyone suggest a more appropriate value, or a way to calculate such?

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#432991

On 10/30/2016 01:11 PM, bitrex wrote:
> I have a MOC3010 optotriac (from da junk box) that I'm trying to use to
> switch about 100VAC from a small inverter brick to a length of EL wire
> about a meter long.
>
> Right now I'm driving the internal infrared LED through a 1k resistor
> from a 3.7 volt supply. The meter shows that the chip is drawing about
> 3mA of current compared to when the pins are disconnected, so I'm
> assuming the LED is turning on, but it doesn't appear to be enough to
> fire the triac when it's hooked up to this load.
>
> Can anyone suggest a more appropriate value, or a way to calculate such?

Ah, wait, I found down at the bottom of the datasheet the MOC3010 needs 
max 15mA, min 8 mA to latch the output at 3 volts. Damn, that's a lot 
for a battery powered app. Time to find a better part...

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#432997

On Sun, 30 Oct 2016 13:13:44 -0400, the renowned bitrex
<bitrex@de.lete.earthlink.net> wrote:

>On 10/30/2016 01:11 PM, bitrex wrote:
>> I have a MOC3010 optotriac (from da junk box) that I'm trying to use to
>> switch about 100VAC from a small inverter brick to a length of EL wire
>> about a meter long.
>>
>> Right now I'm driving the internal infrared LED through a 1k resistor
>> from a 3.7 volt supply. The meter shows that the chip is drawing about
>> 3mA of current compared to when the pins are disconnected, so I'm
>> assuming the LED is turning on, but it doesn't appear to be enough to
>> fire the triac when it's hooked up to this load.
>>
>> Can anyone suggest a more appropriate value, or a way to calculate such?
>
>Ah, wait, I found down at the bottom of the datasheet the MOC3010 needs 
>max 15mA, min 8 mA to latch the output at 3 volts. Damn, that's a lot 
>for a battery powered app. Time to find a better part...


If you know the zero crossing locations you can drive it with a pulse
per cycle, otherwise you can drive it with a pulse train (say 10% duty
cycle) to reduce the power consumption.

I seem to recall ~5mA being about the minimum for that class of part,
and one would have to be reckless indeed to drive it at the minimum
given temperature and aging changes, which are mostly/all negative. 

The Vf for the LED vs. current should also be in the datasheet.

--sp 

-- 
Best regards, 
Spehro Pefhany
Amazon link for AoE 3rd Edition:            http://tinyurl.com/ntrpwu8

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#433003

On 10/30/2016 01:23 PM, Spehro Pefhany wrote:
> On Sun, 30 Oct 2016 13:13:44 -0400, the renowned bitrex
> <bitrex@de.lete.earthlink.net> wrote:
>
>> On 10/30/2016 01:11 PM, bitrex wrote:
>>> I have a MOC3010 optotriac (from da junk box) that I'm trying to use to
>>> switch about 100VAC from a small inverter brick to a length of EL wire
>>> about a meter long.
>>>
>>> Right now I'm driving the internal infrared LED through a 1k resistor
>>> from a 3.7 volt supply. The meter shows that the chip is drawing about
>>> 3mA of current compared to when the pins are disconnected, so I'm
>>> assuming the LED is turning on, but it doesn't appear to be enough to
>>> fire the triac when it's hooked up to this load.
>>>
>>> Can anyone suggest a more appropriate value, or a way to calculate such?
>>
>> Ah, wait, I found down at the bottom of the datasheet the MOC3010 needs
>> max 15mA, min 8 mA to latch the output at 3 volts. Damn, that's a lot
>> for a battery powered app. Time to find a better part...
>
>
> If you know the zero crossing locations you can drive it with a pulse
> per cycle, otherwise you can drive it with a pulse train (say 10% duty
> cycle) to reduce the power consumption.
>
> I seem to recall ~5mA being about the minimum for that class of part,
> and one would have to be reckless indeed to drive it at the minimum
> given temperature and aging changes, which are mostly/all negative.
>
> The Vf for the LED vs. current should also be in the datasheet.
>
> --sp
>

Thanks, I'll try driving it with a pulse train from the uP. Figuring out 
the zero-crossings is a cool idea, but would require sampling the HV 
into the uP's ADC, an exercise I don't have time for at the moment...:)

One more question, I know this setup will work fine for low-speed 
switching, but can the pulse train from the uP be adapted to create a 
dimming or "fading" effect for the strip as well?

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#433005

On Sun, 30 Oct 2016 13:35:03 -0400, the renowned bitrex
<bitrex@de.lete.earthlink.net> wrote:

>
>Thanks, I'll try driving it with a pulse train from the uP. Figuring out 
>the zero-crossings is a cool idea, but would require sampling the HV 
>into the uP's ADC, an exercise I don't have time for at the moment...:)
>
>One more question, I know this setup will work fine for low-speed 
>switching, but can the pulse train from the uP be adapted to create a 
>dimming or "fading" effect for the strip as well?

Not without zero crossing information. 

--sp 

-- 
Best regards, 
Spehro Pefhany
Amazon link for AoE 3rd Edition:            http://tinyurl.com/ntrpwu8

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#433007

On 10/30/2016 01:39 PM, Spehro Pefhany wrote:
> On Sun, 30 Oct 2016 13:35:03 -0400, the renowned bitrex
> <bitrex@de.lete.earthlink.net> wrote:
>
>>
>> Thanks, I'll try driving it with a pulse train from the uP. Figuring out
>> the zero-crossings is a cool idea, but would require sampling the HV
>> into the uP's ADC, an exercise I don't have time for at the moment...:)
>>
>> One more question, I know this setup will work fine for low-speed
>> switching, but can the pulse train from the uP be adapted to create a
>> dimming or "fading" effect for the strip as well?
>
> Not without zero crossing information.
>
> --sp
>

Gotcha, I guess it would work similarly to a triac incandescent lamp 
dimmer that reduces the effective RMS drive voltage by "cutting in" only 
after some delay from the zero-crossing. I wasn't sure if it would work 
the same with a capacitive load like an EL strip.

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#433010

On Sun, 30 Oct 2016 13:39:03 -0400, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

>On Sun, 30 Oct 2016 13:35:03 -0400, the renowned bitrex
><bitrex@de.lete.earthlink.net> wrote:
>
>>
>>Thanks, I'll try driving it with a pulse train from the uP. Figuring out 
>>the zero-crossings is a cool idea, but would require sampling the HV 
>>into the uP's ADC, an exercise I don't have time for at the moment...:)
>>
>>One more question, I know this setup will work fine for low-speed 
>>switching, but can the pulse train from the uP be adapted to create a 
>>dimming or "fading" effect for the strip as well?
>
>Not without zero crossing information. 
>
>--sp 

The bridge rectifier + mosfet thing could probably do PWM dimming
without knowing the power phase. That could get interesting.




-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#433320

On 10/30/2016 01:52 PM, John Larkin wrote:
> On Sun, 30 Oct 2016 13:39:03 -0400, Spehro Pefhany
> <speffSNIP@interlogDOTyou.knowwhat> wrote:
>
>> On Sun, 30 Oct 2016 13:35:03 -0400, the renowned bitrex
>> <bitrex@de.lete.earthlink.net> wrote:
>>
>>>
>>> Thanks, I'll try driving it with a pulse train from the uP. Figuring out
>>> the zero-crossings is a cool idea, but would require sampling the HV
>>> into the uP's ADC, an exercise I don't have time for at the moment...:)
>>>
>>> One more question, I know this setup will work fine for low-speed
>>> switching, but can the pulse train from the uP be adapted to create a
>>> dimming or "fading" effect for the strip as well?
>>
>> Not without zero crossing information.
>>
>> --sp
>
> The bridge rectifier + mosfet thing could probably do PWM dimming
> without knowing the power phase. That could get interesting.
>

It seems the tricky part of using a TRIAC to accomplish dimming is that 
it presents a capacitive load, so with the I and V out-of-phase the 
technique of cutting in the AC voltage some of radians after the zero 
crossing to reduce the effective RMS voltage (as one would in an 
old-fashioned incandescent lamp dimmer) doesn't work properly.

Looks a lot of folks accomplish dimming then by modulating the inverter 
input low voltage, which appears to work but seems like an inefficient 
and clunky solution. And doesn't let you dim strands independently from 
the same inverter brick.

So rectify to pulsed DC and MOSFET? Or use some circuit to make the wire 
look resistive? Or use TRIACs with built in zero-crossing detectors and 
do some kind of "pulse swallowing" modulation?

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#433322

Den tirsdag den 1. november 2016 kl. 17.29.49 UTC+1 skrev bitrex:
> On 10/30/2016 01:52 PM, John Larkin wrote:
> > On Sun, 30 Oct 2016 13:39:03 -0400, Spehro Pefhany
> > <speffSNIP@interlogDOTyou.knowwhat> wrote:
> >
> >> On Sun, 30 Oct 2016 13:35:03 -0400, the renowned bitrex
> >> <bitrex@de.lete.earthlink.net> wrote:
> >>
> >>>
> >>> Thanks, I'll try driving it with a pulse train from the uP. Figuring out
> >>> the zero-crossings is a cool idea, but would require sampling the HV
> >>> into the uP's ADC, an exercise I don't have time for at the moment...:)
> >>>
> >>> One more question, I know this setup will work fine for low-speed
> >>> switching, but can the pulse train from the uP be adapted to create a
> >>> dimming or "fading" effect for the strip as well?
> >>
> >> Not without zero crossing information.
> >>
> >> --sp
> >
> > The bridge rectifier + mosfet thing could probably do PWM dimming
> > without knowing the power phase. That could get interesting.
> >
> 
> It seems the tricky part of using a TRIAC to accomplish dimming is that 
> it presents a capacitive load, so with the I and V out-of-phase the 
> technique of cutting in the AC voltage some of radians after the zero 
> crossing to reduce the effective RMS voltage (as one would in an 
> old-fashioned incandescent lamp dimmer) doesn't work properly.
> 
> Looks a lot of folks accomplish dimming then by modulating the inverter 
> input low voltage, which appears to work but seems like an inefficient 
> and clunky solution. And doesn't let you dim strands independently from 
> the same inverter brick.
> 
> So rectify to pulsed DC and MOSFET? Or use some circuit to make the wire 
> look resistive? Or use TRIACs with built in zero-crossing detectors and 
> do some kind of "pulse swallowing" modulation?

FET inside bridge rectifier or back-to-back fets 

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#433048

"bitrex" <bitrex@de.lete.earthlink.net> wrote in message 
news:dTpRz.12758$AI2.12727@fx04.iad...
> On 10/30/2016 01:11 PM, bitrex wrote:
>> I have a MOC3010 optotriac (from da junk box) that I'm trying to use to
>> switch about 100VAC from a small inverter brick to a length of EL wire
>> about a meter long.
>>
>> Right now I'm driving the internal infrared LED through a 1k resistor
>> from a 3.7 volt supply. The meter shows that the chip is drawing about
>> 3mA of current compared to when the pins are disconnected, so I'm
>> assuming the LED is turning on, but it doesn't appear to be enough to
>> fire the triac when it's hooked up to this load.
>>
>> Can anyone suggest a more appropriate value, or a way to calculate such?
>
> Ah, wait, I found down at the bottom of the datasheet the MOC3010 needs 
> max 15mA, min 8 mA to latch the output at 3 volts. Damn, that's a lot for 
> a battery powered app. Time to find a better part...

There are plenty of MOSFETs that can handle that - presumably your EL rope 
is AC, so the MOSFET will need to be enclosed by a bridge rectifier. That 
probably means isolation will be unavoidable, a basic transistor output opto 
would work, but you can also get MOSFET output as well.

Now I think about it - there's a dual MOSFET output optocoupler for telecoms 
use that can handle AC on its output.

Its non latching - but the triac output only latches for the remainder of 
any half cycle you trigger it on. 

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#433091

On 30.10.16 18:13, bitrex wrote:
> On 10/30/2016 01:11 PM, bitrex wrote:
>> I have a MOC3010 optotriac (from da junk box) that I'm trying to use to
>> switch about 100VAC from a small inverter brick to a length of EL wire
>> about a meter long.
>>
>> Right now I'm driving the internal infrared LED through a 1k resistor
>> from a 3.7 volt supply. The meter shows that the chip is drawing about
>> 3mA of current compared to when the pins are disconnected, so I'm
>> assuming the LED is turning on, but it doesn't appear to be enough to
>> fire the triac when it's hooked up to this load.
>>
>> Can anyone suggest a more appropriate value, or a way to calculate such?
>
> Ah, wait, I found down at the bottom of the datasheet the MOC3010 needs
> max 15mA, min 8 mA to latch the output at 3 volts. Damn, that's a lot
> for a battery powered app. Time to find a better part...
>
jabut... the trigger only needs to be a few microseconds per period?

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#433190

"Sjouke Burry" <burrynulnulfour@ppllaanneett.nnll> wrote in message 
news:5816a366$0$1745$e4fe514c@textnews.kpn.nl...
> On 30.10.16 18:13, bitrex wrote:
>> On 10/30/2016 01:11 PM, bitrex wrote:
>>> I have a MOC3010 optotriac (from da junk box) that I'm trying to use to
>>> switch about 100VAC from a small inverter brick to a length of EL wire
>>> about a meter long.
>>>
>>> Right now I'm driving the internal infrared LED through a 1k resistor
>>> from a 3.7 volt supply. The meter shows that the chip is drawing about
>>> 3mA of current compared to when the pins are disconnected, so I'm
>>> assuming the LED is turning on, but it doesn't appear to be enough to
>>> fire the triac when it's hooked up to this load.
>>>
>>> Can anyone suggest a more appropriate value, or a way to calculate such?
>>
>> Ah, wait, I found down at the bottom of the datasheet the MOC3010 needs
>> max 15mA, min 8 mA to latch the output at 3 volts. Damn, that's a lot
>> for a battery powered app. Time to find a better part...
>>
> jabut... the trigger only needs to be a few microseconds per period?

Not if the load current is less than the holding current.................... 

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#433000

On Sun, 30 Oct 2016 13:11:03 -0400, bitrex
<bitrex@de.lete.earthlink.net> wrote:

>I have a MOC3010 optotriac (from da junk box) that I'm trying to use to 
>switch about 100VAC from a small inverter brick to a length of EL wire 
>about a meter long.
>
>Right now I'm driving the internal infrared LED through a 1k resistor 
>from a 3.7 volt supply. The meter shows that the chip is drawing about 
>3mA of current compared to when the pins are disconnected, so I'm 
>assuming the LED is turning on, but it doesn't appear to be enough to 
>fire the triac when it's hooked up to this load.
>
>Can anyone suggest a more appropriate value, or a way to calculate such?

How about an SSR? They often turn on at 1 mA or less.

Or use a bridge rectifier and a mosfet, which would need picowatts of
gate drive.

Or a latching relay! 




-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#433004

On 10/30/2016 01:28 PM, John Larkin wrote:
> On Sun, 30 Oct 2016 13:11:03 -0400, bitrex
> <bitrex@de.lete.earthlink.net> wrote:
>
>> I have a MOC3010 optotriac (from da junk box) that I'm trying to use to
>> switch about 100VAC from a small inverter brick to a length of EL wire
>> about a meter long.
>>
>> Right now I'm driving the internal infrared LED through a 1k resistor
>>from a 3.7 volt supply. The meter shows that the chip is drawing about
>> 3mA of current compared to when the pins are disconnected, so I'm
>> assuming the LED is turning on, but it doesn't appear to be enough to
>> fire the triac when it's hooked up to this load.
>>
>> Can anyone suggest a more appropriate value, or a way to calculate such?
>
> How about an SSR? They often turn on at 1 mA or less.
>
> Or use a bridge rectifier and a mosfet, which would need picowatts of
> gate drive.

All possibilities, but as I have about 24 hours to complete this 
one-off, it'll have to wait for Version 2.

What's the sweet spot on el-cheapo SSRs to switch 100V RMS at a few 10s 
of mA?

> Or a latching relay!

With infinite gain?

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#433009

On Sun, 30 Oct 2016 13:36:43 -0400, bitrex
<bitrex@de.lete.earthlink.net> wrote:

>On 10/30/2016 01:28 PM, John Larkin wrote:
>> On Sun, 30 Oct 2016 13:11:03 -0400, bitrex
>> <bitrex@de.lete.earthlink.net> wrote:
>>
>>> I have a MOC3010 optotriac (from da junk box) that I'm trying to use to
>>> switch about 100VAC from a small inverter brick to a length of EL wire
>>> about a meter long.
>>>
>>> Right now I'm driving the internal infrared LED through a 1k resistor
>>>from a 3.7 volt supply. The meter shows that the chip is drawing about
>>> 3mA of current compared to when the pins are disconnected, so I'm
>>> assuming the LED is turning on, but it doesn't appear to be enough to
>>> fire the triac when it's hooked up to this load.
>>>
>>> Can anyone suggest a more appropriate value, or a way to calculate such?
>>
>> How about an SSR? They often turn on at 1 mA or less.
>>
>> Or use a bridge rectifier and a mosfet, which would need picowatts of
>> gate drive.
>
>All possibilities, but as I have about 24 hours to complete this 
>one-off, it'll have to wait for Version 2.
>
>What's the sweet spot on el-cheapo SSRs to switch 100V RMS at a few 10s 
>of mA?

You'd have to prowl Digikey for that. We use a couple of 300-volt
SSRs, but they're not cheap.

There are small sensitive-gate triacs around, probably very cheap.

>
>> Or a latching relay!
>
>With infinite gain?

Approximately.


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#433011

On 10/30/2016 01:49 PM, John Larkin wrote:
> On Sun, 30 Oct 2016 13:36:43 -0400, bitrex
> <bitrex@de.lete.earthlink.net> wrote:
>
>> On 10/30/2016 01:28 PM, John Larkin wrote:
>>> On Sun, 30 Oct 2016 13:11:03 -0400, bitrex
>>> <bitrex@de.lete.earthlink.net> wrote:
>>>
>>>> I have a MOC3010 optotriac (from da junk box) that I'm trying to use to
>>>> switch about 100VAC from a small inverter brick to a length of EL wire
>>>> about a meter long.
>>>>
>>>> Right now I'm driving the internal infrared LED through a 1k resistor
>>> >from a 3.7 volt supply. The meter shows that the chip is drawing about
>>>> 3mA of current compared to when the pins are disconnected, so I'm
>>>> assuming the LED is turning on, but it doesn't appear to be enough to
>>>> fire the triac when it's hooked up to this load.
>>>>
>>>> Can anyone suggest a more appropriate value, or a way to calculate such?
>>>
>>> How about an SSR? They often turn on at 1 mA or less.
>>>
>>> Or use a bridge rectifier and a mosfet, which would need picowatts of
>>> gate drive.
>>
>> All possibilities, but as I have about 24 hours to complete this
>> one-off, it'll have to wait for Version 2.
>>
>> What's the sweet spot on el-cheapo SSRs to switch 100V RMS at a few 10s
>> of mA?
>
> You'd have to prowl Digikey for that. We use a couple of 300-volt
> SSRs, but they're not cheap.
>
> There are small sensitive-gate triacs around, probably very cheap.

The cheapest optotriac at Mouser looks like a good candidate:

http://www.mouser.com/ds/2/427/k3020p-67202.pdf

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#433017

bitrex wrote...
>
> The cheapest optotriac at Mouser looks like a good candidate:
> http://www.mouser.com/ds/2/427/k3020p-67202.pdf

 The diode trigger current is 15mA typ, 30mA max.
 Go for a K3023 for 3mA / 5mA max sensitivity.


-- 
 Thanks,
    - Win

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#433008

The MOC3010 needs 15ma to guarantee a reliable trigger.  The diode's forward 
voltage is 1.5V max.
That means the you need to drop 3.7 V - 1.5V = 2.2V by the resistor.
So, the resistor's value needs to be 2.2V / 15ma = 147 ohms.  A 5% value of 
130 or 150 ohms should guarantee that the MOC3010 will trigger the triac.

Dave M


"bitrex" <bitrex@de.lete.earthlink.net> wrote in message 
news:JQpRz.12757$AI2.10239@fx04.iad...
>I have a MOC3010 optotriac (from da junk box) that I'm trying to use to 
>switch about 100VAC from a small inverter brick to a length of EL wire 
>about a meter long.
>
> Right now I'm driving the internal infrared LED through a 1k resistor from 
> a 3.7 volt supply. The meter shows that the chip is drawing about 3mA of 
> current compared to when the pins are disconnected, so I'm assuming the 
> LED is turning on, but it doesn't appear to be enough to fire the triac 
> when it's hooked up to this load.
>
> Can anyone suggest a more appropriate value, or a way to calculate such? 

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#433109

On 2016-10-30, bitrex <bitrex@de.lete.earthlink.net> wrote:
> I have a MOC3010 optotriac (from da junk box) that I'm trying to use to 
> switch about 100VAC from a small inverter brick to a length of EL wire 
> about a meter long.
>
> Right now I'm driving the internal infrared LED through a 1k resistor 
> from a 3.7 volt supply. The meter shows that the chip is drawing about 
> 3mA of current compared to when the pins are disconnected, so I'm 
> assuming the LED is turning on, but it doesn't appear to be enough to 
> fire the triac when it's hooked up to this load.
>
> Can anyone suggest a more appropriate value, or a way to calculate such?


   .-- inverter --- rope --||-------.    ... mosfet could be BJT.
   |                                `-||     with antiparallel diode
  ---                                 || 
   -                                .-|`--- from microcontroller
                                    |
                                   ---
			            -
				       
  it may not be possible to go fully dark.
 
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#433114

On 30/10/2016 17:11, bitrex wrote:
> I have a MOC3010 optotriac (from da junk box) that I'm trying to use to
> switch about 100VAC from a small inverter brick to a length of EL wire
> about a meter long.
>
> Right now I'm driving the internal infrared LED through a 1k resistor
> from a 3.7 volt supply. The meter shows that the chip is drawing about
> 3mA of current compared to when the pins are disconnected, so I'm
> assuming the LED is turning on, but it doesn't appear to be enough to
> fire the triac when it's hooked up to this load.
>
> Can anyone suggest a more appropriate value, or a way to calculate such?

A MOC3012 is more sensitive but please say what is the frequency from 
the inverter? If much over 500Hz then any photo-triac will struggle to 
commutate off after triggering. Check datasheet commutating dV/dt spec.

piglet

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