Date:         Mon, 7 Aug 2017 03:29:43 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Time Delay LED Lighting Circuit
Comments: To: Alistair Bell <albell@shaw.ca>
Comments: cc: Dick Wong <sailingfc@dslextreme.com>
In-Reply-To:  <CAMOH8LL641F+aZf9prw6nk+Wj7fVoeE_LzbgR0oWU6x2_-4xSA@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"

Total price for components in onesies from DigiKey is $1.80 plus shipping.
Not including circuit board, wires etc.

This circuit could be wired up freestanding with reasonable care, I think,
and potted or otherwise protected.  Note that the metal on the back of the
BD433 is connected to the collector and shouldn't touch ground.

BD433 - $0.64
BC547 - $0.22 each.
47uF 16V radial lead aluminum - $0.32
1N4148 diodes in TO-35 packatge and quarter watt carbon film through-hole
resistors ten cents each.

The BD433 is about four cents if you want five thousand or so.  Didn't look
at the rest.

Yrs,
d


On Sun, Aug 6, 2017 at 10:24 PM, David Beierl <dbeierl@attglobal.net> wrote:

> Drat!  D2 polarity is reversed on the schematic, should be pointing toward
> the + rail.  It doesn't conduct until the + line is grounded; then the cap
> discharges through it.
>
> Yrs,
> d
>
> On Sun, Aug 6, 2017 at 10:11 PM, David Beierl <dbeierl@attglobal.net>
> wrote:
>
>> It's the combination of the cap size and R2 size.
>>
>> Increasing R2 value at some point will run into the cap's internal
>> leakage (just like the temp gauge blinker timeout circuit) and fail to time
>> out and/or become excessively sensitive to humidity and board contamination.
>>
>> Yrs,
>> d
>>
>> On Sun, Aug 6, 2017 at 10:03 PM, Alistair Bell <albell@shaw.ca> wrote:
>>
>>> Ok, I'm not going to pretend to know... is it just the cap that
>>> determines delay time?
>>>
>>> Ab
>>>
>>>
>