Reply by Bob Engelhardt●November 27, 20212021-11-27
On 11/25/2021 9:42 PM, Jasen Betts wrote:
> On 2021-11-25, Bob Engelhardt <BobEngelhardt@comcast.net> wrote:
>> ... Any good tricks for seeing non-repetitive events?
>>
>
> long exposure photography on your scope screen.
> take a video recording of the scope
> get a storage oscilloscope.
> use a sound-card and software PC oscilloscope
>
I have an iPhone camera - no shutter control. But I just found a
feature that does a virtual long exposure (Live photos & Effects). I'm
gonna' try it.
Reply by Jasen Betts●November 25, 20212021-11-25
On 2021-11-25, Bob Engelhardt <BobEngelhardt@comcast.net> wrote:
> On 11/22/2021 9:20 PM, Bob Engelhardt wrote:
>> I found this neat soft-start circuit on the eevblog forum. Its neatness
>> is that the gate threshold voltage occurs immediately and then the RC
>> softness kicks in.
>>
>> V+ ________________________ V+
>> |
>> |
>> 1M ___________ V-
>> |___1u___|
>> | |
>> | |--
>> |------|
>> |--
>> |
>> V- ____________|
>>
> ...
>
> OK ... I built this and tried it out. Didn't work as expected & when I
> put my scope (Tek 465) on it, I couldn't see the trace. It's a 1-shot
> sort of event & the scope doesn't have the persistence (let alone
> storage) to see it. Any good tricks for seeing non-repetitive events?
>
> Thanks, Bob
long exposure photography on your scope screen.
take a video recording of the scope
get a storage oscilloscope.
use a sound-card and software PC oscilloscope
--
Jasen.
Reply by Bob Engelhardt●November 25, 20212021-11-25
On 11/22/2021 9:20 PM, Bob Engelhardt wrote:
> I found this neat soft-start circuit on the eevblog forum. Its neatness
> is that the gate threshold voltage occurs immediately and then the RC
> softness kicks in.
>
> V+ ________________________ V+
> |
> |
> 1M ___________ V-
> |___1u___|
> | |
> | |--
> |------|
> |--
> |
> V- ____________|
>
...
OK ... I built this and tried it out. Didn't work as expected & when I
put my scope (Tek 465) on it, I couldn't see the trace. It's a 1-shot
sort of event & the scope doesn't have the persistence (let alone
storage) to see it. Any good tricks for seeing non-repetitive events?
Thanks, Bob
Reply by Jasen Betts●November 24, 20212021-11-24
On 2021-11-24, Bob Engelhardt <BobEngelhardt@comcast.net> wrote:
> On 11/23/2021 2:11 AM, Jasen Betts wrote:
>
>>
>> could do this perhaps?
...
>> | |
>> V-/+ ____________|-->S--'
>>
> That would work ... clever, too. Thanks.
>
> I'm guessing that the "S<" is a Shottky diode. Preferable for the lower
> forward drop?
Yes. mainly to have a lower drop than the substrate diode of the MOSFET.
yes.
--
Jasen.
Reply by Bob Engelhardt●November 24, 20212021-11-24
On 11/23/2021 2:11 AM, Jasen Betts wrote:
>
> could do this perhaps?
>
> __________ V +/-
> .--S<--|
> | |
> | --|
> | |------.
> | --| |
> | |___1u___|
> V+/- ___L______| |
> | |
> | 1M
> 1M |
> | _________L__ V-/+
> |___1u___| |
> | | |
> | |-- |
> |------| |
> |-- |
> | |
> V-/+ ____________|-->S--'
>
>
> maybe add a diode parallel with the 1Ms to make faster resets.
> ...
That would work ... clever, too. Thanks.
I'm guessing that the "S<" is a Shottky diode. Preferable for the lower
forward drop?
Reply by Jasen Betts●November 23, 20212021-11-23
On 2021-11-23, Bob Engelhardt <BobEngelhardt@comcast.net> wrote:
> I found this neat soft-start circuit on the eevblog forum. Its neatness
> is that the gate threshold voltage occurs immediately and then the RC
> softness kicks in.
>
> V+ ________________________ V+
> |
> |
> 1M ___________ V-
> |___1u___|
> | |
> | |--
> |------|
> |--
> |
> V- ____________|
>
>
> As neat as that is, I have a situation where the motor may be run in
> either direction (either polarity on the input) and the soft start
> circuit won't handle that. To use it with either polarity, I plan to
> use 2 of them & isolate with diodes:
>
> _______
> V+/- -x-----D>--| |---------x-----V+/-
> | | | |
> | | |-----x---------V-/+
> V-/+ -----x-<D--|_______| | |
> | | | |
> | | _______ | |
> | |_D>__| |_____| |
> | | | |
> |_____<D__| |_________|
> |_______|
>
> It looks OK to me, but what do I know & I'd like to hear what you think.
> Am I missing anything?
could do this perhaps?
__________ V +/-
.--S<--|
| |
| --|
| |------.
| --| |
| |___1u___|
V+/- ___L______| |
| |
| 1M
1M |
| _________L__ V-/+
|___1u___| |
| | |
| |-- |
|------| |
|-- |
| |
V-/+ ____________|-->S--'
maybe add a diode parallel with the 1Ms to make faster resets.
> BTW - anybody know of software that will do schematics with keyboard
> characters?
None that's worth bothering with.
--
Jasen.
Reply by Bob Engelhardt●November 22, 20212021-11-22
I found this neat soft-start circuit on the eevblog forum. Its neatness
is that the gate threshold voltage occurs immediately and then the RC
softness kicks in.
V+ ________________________ V+
|
|
1M ___________ V-
|___1u___|
| |
| |--
|------|
|--
|
V- ____________|
As neat as that is, I have a situation where the motor may be run in
either direction (either polarity on the input) and the soft start
circuit won't handle that. To use it with either polarity, I plan to
use 2 of them & isolate with diodes:
_______
V+/- -x-----D>--| |---------x-----V+/-
| | | |
| | |-----x---------V-/+
V-/+ -----x-<D--|_______| | |
| | | |
| | _______ | |
| |_D>__| |_____| |
| | | |
|_____<D__| |_________|
|_______|
It looks OK to me, but what do I know & I'd like to hear what you think.
Am I missing anything?
Thanks, Bob
BTW - anybody know of software that will do schematics with keyboard
characters?