Today's Message Index:
----------------------
1. 11:28 AM - Re: Heated Seats (GLEN MATEJCEK)
2. 11:43 AM - Re: Re: Heated Seats (Matthew S. Whiting)
3. 12:10 PM - Re: Re: Heated Seats (Jeff Luckey)
4. 12:48 PM - Re: Re: Heated Seats (Matthew S. Whiting)
5. 02:10 PM - Re: Re: Next generation Crowbar OVM (Robert L. Nuckolls, III)
6. 02:43 PM - Re: Re: Next generation Crowbar OVM (Finn Lassen)
7. 04:42 PM - Re: Re: Next generation Crowbar OVM (Robert L. Nuckolls, III)
Message 1
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| Subject: | RE: Heated Seats |
>
> Hi Jeff-
Years ago I was planning on seat heaters, when someone on the list
commented on how he had them in his car. I think it was a Volvo, but I'm
not positive at this late date. In any case, while using the heater one
day an issue arose. Within something like a minute and a half of having
pulled over, his car was fully afire.
I changed my focus to improving the efficiency of my cockpit heat delivery
and ventilation, as well as making a really tight canopy skirt.
FWIW-
Message 2
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| Subject: | Re: RE: Heated Seats |
I=99m with you. Resistance heaters in a high flex area just seems lik
e asking for trouble.
Sent from my iPad
> On Aug 24, 2023, at 2:31 PM, GLEN MATEJCEK <fly4grins@gmail.com> wrote:
>
> =EF=BB
>> Hi Jeff-
>
> Years ago I was planning on seat heaters, when someone on the list comment
ed on how he had them in his car. I think it was a Volvo, but I'm not posit
ive at this late date. In any case, while using the heater one day an issue
arose. Within something like a minute and a half of having pulled over, hi
s car was fully afire.
> I changed my focus to improving the efficiency of my cockpit heat delivery
and ventilation, as well as making a really tight canopy skirt.
> FWIW-
Message 3
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| Subject: | Re: RE: Heated Seats |
Glenn & Matt,
You mean you don't like it when your ass is literally on fire at 7500 ft at
160kts??? ;)=C2- ( I have nightmares about in-flight fires and trying to
make that emergency decent :(
All kidding aside, that is a valid observation.=C2- The seat heaters are
for a client's airplane and I will definitely pass this along.
On the other hand, I haven't heard of any fires caused by seat heaters in e
xperimental aircraft.=C2- One would think that something like that would
be headline news.=C2- Also, I wonder if the seat materials in an experime
ntal are different from ones found in cars.=C2- You know, fire retardant
foam used in the seat cushions?=C2- Perhaps some questions for the seat c
ushion manufacturer are in order.
Thanks for breaching the subject.
-Jeff
On Thursday, August 24, 2023 at 11:35:04 AM PDT, GLEN MATEJCEK <fly4gri
ns@gmail.com> wrote:
Hi Jeff-
Years ago I was planning on seat heaters, when someone on the list commente
d on how he had them in his car.=C2- I think it was a Volvo, but I'm not
positive at this late date.=C2- In any case, while using the heater one d
ay an issue arose.=C2- Within something like a minute and a half of havin
g pulled over, his car was fully afire.=C2-=C2-I changed my focus to im
proving the efficiency of my cockpit heat delivery and ventilation, as well
as making a really tight canopy skirt.FWIW-=C2-
Message 4
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| Subject: | Re: RE: Heated Seats |
In flight fire is my worst case scenario in an airplane. I think I=99
d rather lose a wing and have it over fairly quickly than slowly roast on th
e way down.
I have not heard of a significant fire hazard either with seat heaters, but t
o me even an infinitesimal risk isn=99t worth it for a feature that is
entirely optional and not even that important most of the time. And I say t
his as someone who lives in a fairly cold winter area. I=99m focusing
on insulating the cabin with aviation approved melamine and trying to seal i
t as well as possible to make the cabin heater as effective as possible.
Sent from my iPad
> On Aug 24, 2023, at 3:12 PM, Jeff Luckey <jluckey@pacbell.net> wrote:
>
> =EF=BB
> Glenn & Matt,
>
> You mean you don't like it when your ass is literally on fire at 7500 ft a
t 160kts??? ;) ( I have nightmares about in-flight fires and trying to make
that emergency decent :(
>
> All kidding aside, that is a valid observation. The seat heaters are for a
client's airplane and I will definitely pass this along.
>
> On the other hand, I haven't heard of any fires caused by seat heaters in e
xperimental aircraft. One would think that something like that would be hea
dline news. Also, I wonder if the seat materials in an experimental are dif
ferent from ones found in cars. You know, fire retardant foam used in the s
eat cushions? Perhaps some questions for the seat cushion manufacturer are i
n order.
>
> Thanks for breaching the subject.
>
> -Jeff
>
> On Thursday, August 24, 2023 at 11:35:04 AM PDT, GLEN MATEJCEK <fly4grins@
gmail.com> wrote:
>
>
> Hi Jeff-
>
> Years ago I was planning on seat heaters, when someone on the list comment
ed on how he had them in his car. I think it was a Volvo, but I'm not posit
ive at this late date. In any case, while using the heater one day an issue
arose. Within something like a minute and a half of having pulled over, hi
s car was fully afire.
> I changed my focus to improving the efficiency of my cockpit heat delivery
and ventilation, as well as making a really tight canopy skirt.
> FWIW-
Message 5
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| Subject: | Re: Next generation Crowbar OVM |
>> > While the FET may indeed be suited to the 'crowbarring' of a
>> circuit breaker, how do we insure that it maintains a saturated,
>> on condition from the time it switches ON until the breaker opens?
>> >
>> > The gate voltage cannot fall below the minimum value for
>> necessary conduction while the breaker is deciding to toss in the
>> towel... probably 15 to 50 milliseconds.
>>
>>Yeah, good point. When the FET turns on, the supply is pulled HARD
>>toward 0V, which kills the FET's gate drive.
>
> Also good eye. Vcc for the electronics will need to be
> diode isolated from the effects of the crowbar pull down.
> The capacitor across Vcc will be large enough to hold
> the crowbar action ACTIVE long enough to trip the breaker.
Your comment prompted further inquiry into suitable
replacements for the SCR I had been using. Don't
know what I entered 'wrong' in the search parameters
but another look produced this little gem:
https://www.ween-semi.com/sites/default/files/2022-02/TYN30-600TF.pdf
Very sensitive gate current (10 mA). Specifically
cited for 'crowbar service'. Price is right too.
I've got some on order.
This illustrates the value of collaborative dialog.
I might well have peddled down the FET pathway
with success as yet to be demonstrated. Your
comment prompted another look into the 'devil-
we-know' technology with what appears to be
a superior solution that's more compatible with
the very low-power, comparator-timer configuration.
Don't know how I missed it the first time at-bat.
I'm headed out with the grandma and grandson for
Oregon to get my little brother married off . . .
and to let grandson stick his toes in the Pacific.
We'll be pretty much out of pocket until Sept 6
although I can peek in from time to time through
the web browser portal.
In the mean time, I'll have plenty of opportunity
to conduct some asphalt engineering. I'll knock
out an ECB to see how well we can make this
fourth generation CBOVM sing, dance and do
dishes.
Thanks for your input!
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 6
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| Subject: | Re: Next generation Crowbar OVM |
On 8/24/2023 5:10 PM, Robert L. Nuckolls, III wrote:
>>> > While the FET may indeed be suited to the 'crowbarring' of a
>>> circuit breaker, how do we insure that it maintains a saturated, on
>>> condition from the time it switches ON until the breaker opens?
>>> >
>>> > The gate voltage cannot fall below the minimum value for necessary
>>> conduction while the breaker is deciding to toss in the towel...
>>> probably 15 to 50 milliseconds.
>>>
>>> Yeah, good point. When the FET turns on, the supply is pulled HARD
>>> toward 0V, which kills the FET's gate drive.
>>
>> Also good eye. Vcc for the electronics will need to be
>> diode isolated from the effects of the crowbar pull down.
>> The capacitor across Vcc will be large enough to hold
>> the crowbar action ACTIVE long enough to trip the breaker.
>
> Your comment prompted further inquiry into suitable
> replacements for the SCR I had been using. Don't
> know what I entered 'wrong' in the search parameters
> but another look produced this little gem:
>
> https://www.ween-semi.com/sites/default/files/2022-02/TYN30-600TF.pdf
>
> Very sensitive gate current (10 mA). Specifically
> cited for 'crowbar service'. Price is right too.
> I've got some on order.
>
> This illustrates the value of collaborative dialog.
> I might well have peddled down the FET pathway
> with success as yet to be demonstrated. Your
> comment prompted another look into the 'devil-
> we-know' technology with what appears to be
> a superior solution that's more compatible with
> the very low-power, comparator-timer configuration.
> Don't know how I missed it the first time at-bat.
>
> I'm headed out with the grandma and grandson for
> Oregon to get my little brother married off . . .
> and to let grandson stick his toes in the Pacific.
>
> We'll be pretty much out of pocket until Sept 6
> although I can peek in from time to time through
> the web browser portal.
>
> In the mean time, I'll have plenty of opportunity
> to conduct some asphalt engineering. I'll knock
> out an ECB to see how well we can make this
> fourth generation CBOVM sing, dance and do
> dishes.
>
> Thanks for your input!
>
>
> Bob . . .
>
I just ordered a couple of these:from DigiKey:
<http://d.digikey.com/dc/mn-w0iJh4uEE_bUitNCuXmOASUNxIUHHNt2ANEnMXZ8ao8FtREfeCqxZHIG6PcZpwZo42yi1ERqBkM2A8mtxTzXrmPTSAj0E8ynXAUrQC1RhTlDxingVDlABHdF0QQzwnppj0Fm-1NciFZh9v1tbaO1O8XM-YLOzSFZfzznYFDY=/MDI4LVNYSy01MDcAAAGNvwOWuiW5uRqm3Op60FCGDici2ZgzptWtRMkKDwD_ASnWyWA722b6JIWD19ubVMRGXlytao4=>
SCT640B
<http://d.digikey.com/dc/mn-w0iJh4uEE_bUitNCuXmOASUNxIUHHNt2ANEnMXZ8ao8FtREfeCqxZHIG6PcZpwZo42yi1ERqBkM2A8mtxTzXrmPTSAj0E8ynXAUrQC1RhTlDxingVDlABHdF0QQzwnppj0Fm-1NciFZh9v1tbaO1O8XM-YLOzSFZfzznYFDY=/MDI4LVNYSy01MDcAAAGNvwOWuiW5uRqm3Op60FCGDici2ZgzptWtRMkKDwD_ASnWyWA722b6JIWD19ubVMRGXlytao4=>
1655-2116-ND
*SCR 600V 40A TO220B*
$2.27 each, more than twice the TYN30-600TF :(
The TYN30-600TF has a lower trigger voltage (1V) compared to the SCT640B
(1.5V) but 35mA gate current but same as the S4025 (1.55V and 35mA)
we're trying to replace.
BTW, I was able to order the MBS4991 on eBay, so still possible to make
the original OVP in small quantities.
Finn
Message 7
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| Subject: | Re: Next generation Crowbar OVM |
>
>1655-2116-ND
>SCR 600V 40A TO220B
>
>$2.27 each, more than twice the TYN30-600TF :(
>
>The TYN30-600TF has a lower trigger voltage (1V) compared to the
>SCT640B (1.5V) but 35mA gate current but same as the S4025 (1.55V
>and 35mA) we're trying to replace.
>
>BTW, I was able to order the MBS4991 on eBay, so still possible to
>make the original OVP in small quantities.
>
>Finn
Let us know how your experiment works out!
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
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