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Simplest way for a go/no-go 2-Stroke Engine Temperature Ind

 
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kjashton(at)vnet.net
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PostPosted: Tue Jan 02, 2018 8:03 am    Post subject: Simplest way for a go/no-go 2-Stroke Engine Temperature Ind Reply with quote

Jared, maybe you could substitute a small (about 10cm X 20cm) voltage meter as sold on ebay. Search for mini voltage meter. You’d have the additional advantage of being able to watch the warmup and you wouldn’t have to calibrate an LED on-off setpoint. They are cheap, I gotta try that on my bike!
-Kent

Quote:
On Jan 2, 2018, at 10:27 AM, Jared Yates <email(at)jaredyates.com> wrote:

It's not good to initiate a takeoff with a 2-stroke engine that isn't warm enough, so I'd like to find or make a circuit that measures the temperature and extinguishes an LED when the temperature reaches a certain threshold. Preferably I'd like to adjust that threshold with software or a potentiometer. The result would be a "wait" light: start the engine, and don't take off until the LED is out. That would also function as a "you forgot to turn off the master" warning, after the flying is done.

My first thought was a type K thermocouple measuring CHT under the spark plug, feeding to a hobbyist micro controller like this:
https://learn.adafruit.com/introducing-trinket
with a thermocouple amplifier like this:
https://www.adafruit.com/product/1778

But since I'm only wanting a simple and binary wait/go indication rather than a readout in degrees, I wonder if the above plan is going a little overboard. The electrical system has an 18.5 volt battery for starting, with no onboard charging, so energy consumption is a minor consideration. Tiny size, durability, and reliability are high priorities.

Does anyone have an idea for a simpler design, or better yet, is someone already selling one?



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ceengland7(at)gmail.com
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PostPosted: Tue Jan 02, 2018 8:31 am    Post subject: Simplest way for a go/no-go 2-Stroke Engine Temperature Ind Reply with quote

On 1/2/2018 9:27 AM, Jared Yates wrote:
Quote:
It's not good to initiate a takeoff with a 2-stroke engine that isn't
warm enough, so I'd like to find or make a circuit that measures the
temperature and extinguishes an LED when the temperature reaches a
certain threshold. Preferably I'd like to adjust that threshold with
software or a potentiometer. The result would be a "wait" light: start
the engine, and don't take off until the LED is out. That would also
function as a "you forgot to turn off the master" warning, after the
flying is done.

My first thought was a type K thermocouple measuring CHT under the
spark plug, feeding to a hobbyist micro controller like this:
https://learn.adafruit.com/introducing-trinket
with a thermocouple amplifier like this:
https://www.adafruit.com/product/1778

But since I'm only wanting a simple and binary wait/go indication
rather than a readout in degrees, I wonder if the above plan is going
a little overboard. The electrical system has an 18.5 volt battery for
starting, with no onboard charging, so energy consumption is a minor
consideration. Tiny size, durability, and reliability are high priorities.

Does anyone have an idea for a simpler design, or better yet, is
someone already selling one?

My 1st thought is that the 'forgot' mode probably won't be effective (at

least for me), since it takes time for the heads to cool down. I know
I'd be likely to walk away before the light came on.

2nd thought is that since I'd want CHT gauges anyway, why not just use
them? I'd be sitting in the plane with the engine running, looking at
the instruments, so why not just look at the CHT? No power required, no
extra instrument.

If you really want the light, an LM34 feeding a comparator circuit (op
amp and some resistors) would work.

Charlie

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ceengland7(at)gmail.com
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PostPosted: Tue Jan 02, 2018 9:58 am    Post subject: Simplest way for a go/no-go 2-Stroke Engine Temperature Ind Reply with quote

Any temp sensor that you use will need to be in contact with the cyl,
unless you want to use a laser thermometer.

The TI doc describes soldering or gluing the LM34 to...whatever...., so
you could use a metal case version, solder it to a bolt or pipe thread
adapter that fits the CHT fitting in the head, and screw it in.

http://www.ti.com/product/LM34/datasheet/layout#SNIS1613881

Just saw one possible limitation for the LM34; max operating temp is
300F. You might be able to work around that by mounting it on a fin,
near the edge, instead of directly to the head. You'd need to
'calibrate' the temp delta between actual head temp & the temp at the
edge of the fin, & set your trigger point based on that.

On 1/2/2018 11:24 AM, Jared Yates wrote:
Quote:

<email(at)jaredyates.com>

Thanks Charlie, this is a foot launch ultralight with no panel, so
pilot viewing space is especially premium. Does the LM34 need to be in
contact with the cylinder? I wonder how to best accomplish that,
mechanically speaking.
On January 2, 2018 11:37:25 Charlie England <ceengland7(at)gmail.com> wrote:

>
> <ceengland7(at)gmail.com>
>
> On 1/2/2018 9:27 AM, Jared Yates wrote:
>> It's not good to initiate a takeoff with a 2-stroke engine that isn't
>> warm enough, so I'd like to find or make a circuit that measures the
>> temperature and extinguishes an LED when the temperature reaches a
>> certain threshold. Preferably I'd like to adjust that threshold with
>> software or a potentiometer. The result would be a "wait" light: start
>> the engine, and don't take off until the LED is out. That would also
>> function as a "you forgot to turn off the master" warning, after the
>> flying is done.
>>
>> My first thought was a type K thermocouple measuring CHT under the
>> spark plug, feeding to a hobbyist micro controller like this:
>> https://learn.adafruit.com/introducing-trinket
>> with a thermocouple amplifier like this:
>> https://www.adafruit.com/product/1778
>>
>> But since I'm only wanting a simple and binary wait/go indication
>> rather than a readout in degrees, I wonder if the above plan is going
>> a little overboard. The electrical system has an 18.5 volt battery for
>> starting, with no onboard charging, so energy consumption is a minor
>> consideration. Tiny size, durability, and reliability are high
>> priorities.
>>
>> Does anyone have an idea for a simpler design, or better yet, is
>> someone already selling one?
>>
> My 1st thought is that the 'forgot' mode probably won't be effective (at
> least for me), since it takes time for the heads to cool down. I know
> I'd be likely to walk away before the light came on.
>
> 2nd thought is that since I'd want CHT gauges anyway, why not just use
> them? I'd be sitting in the plane with the engine running, looking at
> the instruments, so why not just look at the CHT? No power required, no
> extra instrument.
>
> If you really want the light, an LM34 feeding a comparator circuit (op
> amp and some resistors) would work.
>
> Charlie


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Joined: 28 Mar 2008
Posts: 1206
Location: Riley TWP Michigan

PostPosted: Tue Jan 02, 2018 10:26 am    Post subject: Re: Simplest way for a go/no-go 2-Stroke Engine Temperature Reply with quote

Perhaps some kind of temperature switch would work?
https://www.omega.com/pptst/TSW-TT.html


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