[TriEmbed] Need help with a beginner circuit design

Thu Oct 29 07:24:11 CDT 2015

More answers and insight...

I don't want to annoy the forum with too many details, but I'm happy to
provide them.  This is actually a prototype of a product I'd like to sell
on a KickStarter eventually (if it works...)- although my wife still thinks
this is a hobby.  She's probably right.

The flashing LED and beeping piezo speaker are pretty easy to do with a 555
timer. I also need around 80Vdc, pulsed about twice per second.  The
current can be extremely low- just 1 mA or less.   The goal is a simple
electric field in salt water to annoy fishes, so ripple/noise doesn't
matter (no need to rectify it or smooth it with caps).  I've seen designs
for stun guns that use a 555 timer output into an audio transformer to step
up the voltage to 10s of thousands of volts.  That would work, but since I
only need 80 Vdc, someone else recommended the MAX1771 chip and built a
quick prototype using that for me.  It also works (and I tested it).
Bottom line- it just needs to be cheap and easy.

Once the design is roughed out, I could still use some help actually
building the thing in a PVC pipe. Therefore, if someone would like to pitch
in, I'd be happy to buy you coffee/lunch/dinner and talk through the whole
thing.  If we get this built, I'll present it at a meeting for all of you
to chuckle at.

Meanwhile, my Bitcoin miner arrives tomorrow...  so you KNOW I'm crazy...

db

On Wed, Oct 28, 2015 at 10:42 AM, Brian via TriEmbed <triembed at triembed.org>
wrote:

> Hi Dave,
>
> Let me echo what others have said, this is a fine forum for your inquiry.
> So: Where is your high voltage coming from?  Are you planning to generate
> it from the same battery that is powering the rest of the circuit?
>
> I'm not sure the MAX1771 is going to meet your needs, if you're looking
> for 80VDC.  I'd suggest instead another 555 astable vibrator driving the
> 8-ohm side of a 8/1000-ohm audio matching transformer.  There's some Ohm's
> Law and transformer math to be done to get just the voltage you want, but
> the basic idea is the 555 chops your battery voltage (9v?), then the
> matching transformer steps it up.  On the output side, you'd outfit a
> rectifier and some tank capacitors to smooth it back out to DC.
>
> Some important considerations:
>
> How steady do you need your HV to be?  Can you tolerate some ripple?
>
> How important is the actual HV potential?  Is 80VDC an important target or
> could it be higher than that?
>
> As the HV is switched on/off, can your application handle it ramping
> rather than switching?
>
> As an aside, out of a sense of due diligence, does your design include
> appropriate measures to keep the HV out of reach?
>
> -B
>
> On 10/27/2015 6:55 PM, Dave Buster via TriEmbed wrote:
>
>> Hi-
>> I'm a long-time lurker on this email, but I'm not active.
>>
>> It's been many, many years since I did Industrial engineering at NC
>> State, and I've mostly been doing data communications and cyber security
>> since then. In other words.... I'm no longer hands on. I don't even know
>> how to solder any more.
>>
>> sigh.  This is embarrassing..
>>
>> Now I have a need to design a build a simple analog circuit for a hobby
>> of mine, and I'm getting stumped.  I'm wondering if someone has some
>> time to give me a few pointers and/or help me with the design.
>>
>> The battery-powered circuit will be very simple.  I need to flash an LED
>> a couple of times per second (I got that working with a 555 timer), then
>> I need to send beeps to a little piezo speaker (I'm still working on
>> that), and finally, I need to pulse a high-voltage/low-current DC signal
>> about twice per second.  I'm thinking of using a max1771 DC-DC converter
>> for that.  ...and I'm in over my head.
>>
>> I won't be able to make it to the November meeting, but would it be
>> possible to get someone to spare an hour some other evening to discuss
>> this?
>>
>> Anyone want to volunteer to help a life-long learner?
>>
>> Here is an email account I don't use very much, but I'll be checking it:
>>
>> dave at tritonsharksignal.com <mailto:dave at tritonsharksignal.com>
>>
>> Also, if this is not appropriate for this email thread, my apologies.
>>
>> thanks!
>>
>>
>>
>> --
>> Dave Buster
>>
>> KK4ELT on 2 meters
>> Never look at the trombones, it only encourages them.
>> *Ri
>> <
>> http://t.sidekickopen23.com/e1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XX45vMtjYVQZgwH64R1y4W8r4TLx56dPn8f5RTxgR02?t=http%3A%2F%2Fwww.brainyquote.com%2Fquotes%2Fauthors%2Fr%2Frichard_wagner.html&si=4964982235594752&pi=6f98b148-9f74-482e-d75c-f87f6847e43c
>> >chard
>> Strauss*
>>
>>
>>
>>
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>>
>>
>
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-- 
Dave Buster

KK4ELT on 2 meters

Never look at the trombones, it only encourages them.
*Ri
<http://t.sidekickopen23.com/e1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XX45vMtjYVQZgwH64R1y4W8r4TLx56dPn8f5RTxgR02?t=http%3A%2F%2Fwww.brainyquote.com%2Fquotes%2Fauthors%2Fr%2Frichard_wagner.html&si=4964982235594752&pi=fb1b59c7-833f-48a2-c3b9-83810eda23b0>chard
Strauss*
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