[CQ-Contest] Mk2R+ optocouplers

Ken K6MR k6mr at outlook.com
Thu Jun 10 09:21:25 EDT 2021

Vf varies a bit from 1.2 V typical @ If = 10 mA, down to 1.0 V typical @ If = 0.3 mA.  You’d think these things would last forever given the absolute max If is 30 mA.

Interesting point though.  I didn’t look to see which one has the max frequency or possibly time of use.  I would guess it would depend somewhat on what particular configuration is being used.

Ken K6MR

From: David Gilbert<mailto:ab7echo at gmail.com>
Sent: Thursday, June 10, 2021 05:15
To: cq-contest at contesting.com<mailto:cq-contest at contesting.com>
Subject: Re: [CQ-Contest] Mk2R+ optocouplers

I was kind of sloppy there.  Given the Vf of an infrared LED, the drive
current would be less than 4 milliamps.

Dave   AB7E

On 6/8/2021 11:30 PM, David Gilbert wrote:
> Yeah, that would be 5 milliamps for all of them, which certainly is
> not an excessive amount of drive current.  Most application notes for
> optocouplers tended to spec about 10 milliamps for a typical
> application, and as best I can remember 50 milliamps was often the max
> rating.  If those optocouplers were degrading at 5 milliamps they
> really had poor quality LEDs in them.
> I still don't buy the idea that the lower speed slots should make much
> difference, though.  I can't think of any reason why speed should make
> a difference in LED lifetime at 5 milliamps unless those slots simply
> were activated significantly more often ... higher duty cycle, not
> higher speed.
> 73,
> Dave   AB7E
> On 6/8/2021 10:19 PM, Ken K6MR wrote:
>> From the info I have it looks like they are all driven through a 1k
>> resistor, supply voltage is either the USB 5V bus or the system 5V
>> bus.  Drive current looks to be well below the max shown on the data
>> sheet.
>> My unit is pretty old and has all Fairchild (white devices).
>> Ken K6MR

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