# Photovoltaic isolator

## Ask a question - edaboard.com

elektroda.net NewsGroups Forum Index - Electronics Design - Photovoltaic isolator

Goto page 1, 2  Next

Clive Arthur
Guest

Fri Jan 06, 2017 12:42 am

I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various solutions,
but I'd like to use a 'solar cell' to supply isolated power.

It's too much power for normal photovoltaic isolators by some orders of
magnitude, so I'm considering using one or more photovoltaic cells with
one or more LEDs shining on them. It's all in an enclosure, so there's
no significant ambient light. The cell(s) could be several square
centimeters area. I like this arrangement as the isolation isn't in any
doubt - there could be centimetres of gap.

What sort of size cells would I need for around 30mW? I guess blue LEDs
would be best? An efficiency of 1% (a 3W input) would be fine, even a
bit less. Just musing at the moment and if anyone has any ball-park
feelings or experience that would be good.

Cheers
--
Clive

Guest

Fri Jan 06, 2017 12:42 am

On Thursday, January 5, 2017 at 12:42:48 PM UTC-5, Clive Arthur wrote:
Quote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various solutions,
but I'd like to use a 'solar cell' to supply isolated power.

It's too much power for normal photovoltaic isolators by some orders of
magnitude, so I'm considering using one or more photovoltaic cells with
one or more LEDs shining on them. It's all in an enclosure, so there's
no significant ambient light. The cell(s) could be several square
centimeters area. I like this arrangement as the isolation isn't in any
doubt - there could be centimetres of gap.

What sort of size cells would I need for around 30mW? I guess blue LEDs
would be best? An efficiency of 1% (a 3W input) would be fine, even a
bit less. Just musing at the moment and if anyone has any ball-park
feelings or experience that would be good.

Cheers
--
Clive

There are high isolation DC-DC converters out there, not cheap, but ultimately superior to a photvoltaic system.
http://www.mouser.com/search/Refine.aspx?Keyword=164194258&Ns=Pricing%7c0&FS=True&Ntk=P_MarCom

Guest

Fri Jan 06, 2017 12:42 am

Den torsdag den 5. januar 2017 kl. 22.42.58 UTC+1 skrev John Larkin:
Quote:
On Thu, 5 Jan 2017 14:46:04 -0500, bitrex

On 01/05/2017 01:53 PM, John Larkin wrote:
On Thu, 5 Jan 2017 10:24:01 -0800 (PST),
bloggs.fredbloggs.fred_at_gmail.com wrote:

On Thursday, January 5, 2017 at 12:42:48 PM UTC-5, Clive Arthur wrote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various solutions,
but I'd like to use a 'solar cell' to supply isolated power.

It's too much power for normal photovoltaic isolators by some orders of
magnitude, so I'm considering using one or more photovoltaic cells with
one or more LEDs shining on them. It's all in an enclosure, so there's
no significant ambient light. The cell(s) could be several square
centimeters area. I like this arrangement as the isolation isn't in any
doubt - there could be centimetres of gap.

What sort of size cells would I need for around 30mW? I guess blue LEDs
would be best? An efficiency of 1% (a 3W input) would be fine, even a
bit less. Just musing at the moment and if anyone has any ball-park
feelings or experience that would be good.

Cheers
--
Clive

There are high isolation DC-DC converters out there, not cheap, but ultimately superior to a photvoltaic system.
http://www.mouser.com/search/Refine.aspx?Keyword=164194258&Ns=Pricing%7c0&FS=True&Ntk=P_MarCom

A home-made inductive coupling thing wouldn't be difficult. It could
work through a piece of plexiglas for visible isolation, or just be
traces on opposite sides of a PC board. That could be really cheap in
production.

Or wind a ferrite toroid to make a transformer, and use really well
insulated wire.

But as you say, it's a lot easier to buy an appropriate dc/dc
converter.

For uA of current using a stack of photodiode optocouplers could work,
but for mA inductive coupling is likely the way to go.

The Starbucks near me has those "Powermat" chargers where you stick an
inductor ring to your phone's charging port and lay it on the inductor
ring on the table; I guess they chop the AC up to a high enough freq
that air makes a decent enough core, and a loop only slightly larger
than a quarter can transfer enough energy to charge up a smartphone in
under an hour

Let's spread the rumor that the field will cause warts or insanity or
something.

the promise of wireless power seems to be able to cause some forms of insanity

https://ubeam.com/technology/

https://youtu.be/ukgnU2aXM2c?t=14m21s

Tim Wescott
Guest

Fri Jan 06, 2017 12:58 am

On Thu, 05 Jan 2017 17:42:44 +0000, Clive Arthur wrote:

Quote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various solutions,
but I'd like to use a 'solar cell' to supply isolated power.

It's too much power for normal photovoltaic isolators by some orders of
magnitude, so I'm considering using one or more photovoltaic cells with
one or more LEDs shining on them. It's all in an enclosure, so there's
no significant ambient light. The cell(s) could be several square
centimeters area. I like this arrangement as the isolation isn't in any
doubt - there could be centimetres of gap.

What sort of size cells would I need for around 30mW? I guess blue LEDs
would be best? An efficiency of 1% (a 3W input) would be fine, even a
bit less. Just musing at the moment and if anyone has any ball-park
feelings or experience that would be good.

It seems like a good idea overall, if your 1% figure is correct. 1%
sounds like a good minimum, don't fall over if you do better. Note,
however, that anything I say here could be wronger than wrong, so take
them all as suggestions for things to test.

I'm pretty sure that the physics of photovoltaics are such that once the
photon smacking into a silicon atom has more energy than the material's
band gap, you get one and only one electron bumped up to the conduction
band for each photon. Assuming that LED energy efficiencies are roughly
similar across the board, you may be better with IR or deep red LEDs than
with blue ones because each photon will come at a lower energy cost.

You probably already know this, but shop around for your emitters and
photovoltaic arrays -- efficiencies vary wildly, and you definitely want
the most bang for your buck here.

I think I'd start with a photovoltaic array that can deliver 100mA at 3V
in full sun -- expecting your artificial light source to have about
1/10th that intensity seems wise. Beyond that, experiment, experiment,
experiment.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

whit3rd
Guest

Fri Jan 06, 2017 1:32 am

On Thursday, January 5, 2017 at 9:42:48 AM UTC-8, Clive Arthur wrote:
Quote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various solutions,
but I'd like to use a 'solar cell' to supply isolated power.

What sort of size cells would I need for around 30mW? I guess blue LEDs
would be best?

Not blue;; go for infrared. The sensitivity peak for silicon is 900-1000 nm,
and blue (420 nm) loses by a factor of two or three.

<http://www.bentham.co.uk/pdf/PV_Technical_Note.pdf>

The mass-produced remote control LEDs are possibly your best bet;
perhaps Vishay TSAL6100. They will probably need some heatsinking,
if the rated 100 mA is applied.

John Larkin
Guest

Fri Jan 06, 2017 1:53 am

On Thu, 5 Jan 2017 10:24:01 -0800 (PST),
bloggs.fredbloggs.fred_at_gmail.com wrote:

Quote:
On Thursday, January 5, 2017 at 12:42:48 PM UTC-5, Clive Arthur wrote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various solutions,
but I'd like to use a 'solar cell' to supply isolated power.

It's too much power for normal photovoltaic isolators by some orders of
magnitude, so I'm considering using one or more photovoltaic cells with
one or more LEDs shining on them. It's all in an enclosure, so there's
no significant ambient light. The cell(s) could be several square
centimeters area. I like this arrangement as the isolation isn't in any
doubt - there could be centimetres of gap.

What sort of size cells would I need for around 30mW? I guess blue LEDs
would be best? An efficiency of 1% (a 3W input) would be fine, even a
bit less. Just musing at the moment and if anyone has any ball-park
feelings or experience that would be good.

Cheers
--
Clive

There are high isolation DC-DC converters out there, not cheap, but ultimately superior to a photvoltaic system.
http://www.mouser.com/search/Refine.aspx?Keyword=164194258&Ns=Pricing%7c0&FS=True&Ntk=P_MarCom

A home-made inductive coupling thing wouldn't be difficult. It could
work through a piece of plexiglas for visible isolation, or just be
traces on opposite sides of a PC board. That could be really cheap in
production.

Or wind a ferrite toroid to make a transformer, and use really well
insulated wire.

But as you say, it's a lot easier to buy an appropriate dc/dc
converter.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Winfield Hill
Guest

Fri Jan 06, 2017 2:20 am

Clive Arthur wrote...
Quote:

I want to run a microcontroller circuit at about 3V 10mA
on the high side of a several kilovolt supply. I know
there are various solutions, but I'd like to use a
'solar cell' to supply isolated power.

A home-made transformer is completely practical.
I made a 0 to 250V supply, floating on top of 15kV,
using a simple TL494 driving a 1:1:10 transformer
at 50kHz. I used a 0.47-inch dia core and machined
a special two-section bobbin, with 1-inch inner dia,
giving 0.25-in insulation. The two sections were
separated by 0.20 in, overall bobbin length 0.8 in.
This performed flawlessly. (The feedback scheme I
chose for the supply was a bit dicey, requiring two
30kV 150M resistors, with considerable care for the
mounting and insulating.) Reference RIS-623.

--
Thanks,
- Win

bitrex
Guest

Fri Jan 06, 2017 2:46 am

On 01/05/2017 01:53 PM, John Larkin wrote:
Quote:
On Thu, 5 Jan 2017 10:24:01 -0800 (PST),
bloggs.fredbloggs.fred_at_gmail.com wrote:

On Thursday, January 5, 2017 at 12:42:48 PM UTC-5, Clive Arthur wrote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various solutions,
but I'd like to use a 'solar cell' to supply isolated power.

It's too much power for normal photovoltaic isolators by some orders of
magnitude, so I'm considering using one or more photovoltaic cells with
one or more LEDs shining on them. It's all in an enclosure, so there's
no significant ambient light. The cell(s) could be several square
centimeters area. I like this arrangement as the isolation isn't in any
doubt - there could be centimetres of gap.

What sort of size cells would I need for around 30mW? I guess blue LEDs
would be best? An efficiency of 1% (a 3W input) would be fine, even a
bit less. Just musing at the moment and if anyone has any ball-park
feelings or experience that would be good.

Cheers
--
Clive

There are high isolation DC-DC converters out there, not cheap, but ultimately superior to a photvoltaic system.
http://www.mouser.com/search/Refine.aspx?Keyword=164194258&Ns=Pricing%7c0&FS=True&Ntk=P_MarCom

A home-made inductive coupling thing wouldn't be difficult. It could
work through a piece of plexiglas for visible isolation, or just be
traces on opposite sides of a PC board. That could be really cheap in
production.

Or wind a ferrite toroid to make a transformer, and use really well
insulated wire.

But as you say, it's a lot easier to buy an appropriate dc/dc
converter.

For uA of current using a stack of photodiode optocouplers could work,
but for mA inductive coupling is likely the way to go.

The Starbucks near me has those "Powermat" chargers where you stick an
inductor ring to your phone's charging port and lay it on the inductor
ring on the table; I guess they chop the AC up to a high enough freq
that air makes a decent enough core, and a loop only slightly larger
than a quarter can transfer enough energy to charge up a smartphone in
under an hour

Tim Wescott
Guest

Fri Jan 06, 2017 3:20 am

On Thu, 05 Jan 2017 14:46:04 -0500, bitrex wrote:

Quote:
On 01/05/2017 01:53 PM, John Larkin wrote:
On Thu, 5 Jan 2017 10:24:01 -0800 (PST),
bloggs.fredbloggs.fred_at_gmail.com wrote:

On Thursday, January 5, 2017 at 12:42:48 PM UTC-5, Clive Arthur wrote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various
solutions, but I'd like to use a 'solar cell' to supply isolated
power.

It's too much power for normal photovoltaic isolators by some orders
of magnitude, so I'm considering using one or more photovoltaic cells
with one or more LEDs shining on them. It's all in an enclosure, so
there's no significant ambient light. The cell(s) could be several
square centimeters area. I like this arrangement as the isolation
isn't in any doubt - there could be centimetres of gap.

What sort of size cells would I need for around 30mW? I guess blue
LEDs would be best? An efficiency of 1% (a 3W input) would be fine,
even a bit less. Just musing at the moment and if anyone has any
ball-park feelings or experience that would be good.

Cheers --
Clive

There are high isolation DC-DC converters out there, not cheap, but
ultimately superior to a photvoltaic system.
http://www.mouser.com/search/Refine.aspx?Keyword=164194258&Ns=Pricing%
7c0&FS=True&Ntk=P_MarCom

A home-made inductive coupling thing wouldn't be difficult. It could
work through a piece of plexiglas for visible isolation, or just be
traces on opposite sides of a PC board. That could be really cheap in
production.

Or wind a ferrite toroid to make a transformer, and use really well
insulated wire.

But as you say, it's a lot easier to buy an appropriate dc/dc
converter.

For uA of current using a stack of photodiode optocouplers could work,
but for mA inductive coupling is likely the way to go.

The Starbucks near me has those "Powermat" chargers where you stick an
inductor ring to your phone's charging port and lay it on the inductor
ring on the table; I guess they chop the AC up to a high enough freq
that air makes a decent enough core, and a loop only slightly larger
than a quarter can transfer enough energy to charge up a smartphone in
under an hour

It's a few hundred kHz, AFAIK.

And yes, it may work better to deliver 10mA at 3V. But it's boring -- I
think Clive should go with the glowing things.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

Tim Wescott
Guest

Fri Jan 06, 2017 3:22 am

On Thu, 05 Jan 2017 14:20:38 -0600, Tim Wescott wrote:

Quote:
On Thu, 05 Jan 2017 14:46:04 -0500, bitrex wrote:

On 01/05/2017 01:53 PM, John Larkin wrote:
On Thu, 5 Jan 2017 10:24:01 -0800 (PST),
bloggs.fredbloggs.fred_at_gmail.com wrote:

On Thursday, January 5, 2017 at 12:42:48 PM UTC-5, Clive Arthur
wrote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various
solutions, but I'd like to use a 'solar cell' to supply isolated
power.

It's too much power for normal photovoltaic isolators by some orders
of magnitude, so I'm considering using one or more photovoltaic
cells with one or more LEDs shining on them. It's all in an
enclosure, so there's no significant ambient light. The cell(s)
could be several square centimeters area. I like this arrangement
as the isolation isn't in any doubt - there could be centimetres of
gap.

What sort of size cells would I need for around 30mW? I guess blue
LEDs would be best? An efficiency of 1% (a 3W input) would be fine,
even a bit less. Just musing at the moment and if anyone has any
ball-park feelings or experience that would be good.

Cheers --
Clive

There are high isolation DC-DC converters out there, not cheap, but
ultimately superior to a photvoltaic system.
http://www.mouser.com/search/Refine.aspx?Keyword=164194258&Ns=Pricing
%
7c0&FS=True&Ntk=P_MarCom

A home-made inductive coupling thing wouldn't be difficult. It could
work through a piece of plexiglas for visible isolation, or just be
traces on opposite sides of a PC board. That could be really cheap in
production.

Or wind a ferrite toroid to make a transformer, and use really well
insulated wire.

But as you say, it's a lot easier to buy an appropriate dc/dc
converter.

For uA of current using a stack of photodiode optocouplers could work,
but for mA inductive coupling is likely the way to go.

The Starbucks near me has those "Powermat" chargers where you stick an
inductor ring to your phone's charging port and lay it on the inductor
ring on the table; I guess they chop the AC up to a high enough freq
that air makes a decent enough core, and a loop only slightly larger
than a quarter can transfer enough energy to charge up a smartphone in
under an hour

It's a few hundred kHz, AFAIK.

And yes, it may work better to deliver 10mA at 3V. But it's boring -- I
think Clive should go with the glowing things.

If you do it all on one circuit board (how much isolation is 1/16" FR-4
worth?) then you can vastly increase efficiency by using stick-on ferrite
plates, available from DigiKey as EMI reduction thingies.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

bitrex
Guest

Fri Jan 06, 2017 3:32 am

On 01/05/2017 03:20 PM, Tim Wescott wrote:
Quote:
On Thu, 05 Jan 2017 14:46:04 -0500, bitrex wrote:

On 01/05/2017 01:53 PM, John Larkin wrote:
On Thu, 5 Jan 2017 10:24:01 -0800 (PST),
bloggs.fredbloggs.fred_at_gmail.com wrote:

On Thursday, January 5, 2017 at 12:42:48 PM UTC-5, Clive Arthur wrote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various
solutions, but I'd like to use a 'solar cell' to supply isolated
power.

It's too much power for normal photovoltaic isolators by some orders
of magnitude, so I'm considering using one or more photovoltaic cells
with one or more LEDs shining on them. It's all in an enclosure, so
there's no significant ambient light. The cell(s) could be several
square centimeters area. I like this arrangement as the isolation
isn't in any doubt - there could be centimetres of gap.

What sort of size cells would I need for around 30mW? I guess blue
LEDs would be best? An efficiency of 1% (a 3W input) would be fine,
even a bit less. Just musing at the moment and if anyone has any
ball-park feelings or experience that would be good.

Cheers --
Clive

There are high isolation DC-DC converters out there, not cheap, but
ultimately superior to a photvoltaic system.
http://www.mouser.com/search/Refine.aspx?Keyword=164194258&Ns=Pricing%
7c0&FS=True&Ntk=P_MarCom

A home-made inductive coupling thing wouldn't be difficult. It could
work through a piece of plexiglas for visible isolation, or just be
traces on opposite sides of a PC board. That could be really cheap in
production.

Or wind a ferrite toroid to make a transformer, and use really well
insulated wire.

But as you say, it's a lot easier to buy an appropriate dc/dc
converter.

For uA of current using a stack of photodiode optocouplers could work,
but for mA inductive coupling is likely the way to go.

The Starbucks near me has those "Powermat" chargers where you stick an
inductor ring to your phone's charging port and lay it on the inductor
ring on the table; I guess they chop the AC up to a high enough freq
that air makes a decent enough core, and a loop only slightly larger
than a quarter can transfer enough energy to charge up a smartphone in
under an hour

It's a few hundred kHz, AFAIK.

And yes, it may work better to deliver 10mA at 3V. But it's boring -- I
think Clive should go with the glowing things.

SparkFun has some itty-bitty solar panels for about a buck fifty each,
but their maximum power point looks like about 40uA at 250mV, so it'll
take quite a stack to hit 10mA.

Since he's got kV available, why not wrap a gas discharge/neon tube in
some strips of PV sheet?

George Herold
Guest

Fri Jan 06, 2017 4:13 am

On Thursday, January 5, 2017 at 12:42:48 PM UTC-5, Clive Arthur wrote:
Quote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various solutions,
but I'd like to use a 'solar cell' to supply isolated power.

It's too much power for normal photovoltaic isolators by some orders of
magnitude, so I'm considering using one or more photovoltaic cells with
one or more LEDs shining on them. It's all in an enclosure, so there's
no significant ambient light. The cell(s) could be several square
centimeters area. I like this arrangement as the isolation isn't in any
doubt - there could be centimetres of gap.

What sort of size cells would I need for around 30mW? I guess blue LEDs
would be best? An efficiency of 1% (a 3W input) would be fine, even a
bit less. Just musing at the moment and if anyone has any ball-park
feelings or experience that would be good.

Cheers
--
Clive

Can you suck power off the HV and ouput/input via
an optoisolator?
Use a battery? (You have to remember to turn
off the HV before changing the battery...
speaking from experience.)
As Tim and others said I've gotten more photons
from IR leds, you are going to have to stack several
photo cells in series to get to 3V. 10mA each.
LED's are not all that efficient in turning electrons
into light. A diode laser might be better.
We use these ~70mW ones that would give ~
35mA (~ 0.5A/W).

(OK this raises an interesting question,
why not blue lasers for lighting?
(blast 'em into a phosphor prism thing-a-ma-bob.)

George H.

John Larkin
Guest

Fri Jan 06, 2017 4:42 am

On Thu, 5 Jan 2017 14:46:04 -0500, bitrex

Quote:
On 01/05/2017 01:53 PM, John Larkin wrote:
On Thu, 5 Jan 2017 10:24:01 -0800 (PST),
bloggs.fredbloggs.fred_at_gmail.com wrote:

On Thursday, January 5, 2017 at 12:42:48 PM UTC-5, Clive Arthur wrote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various solutions,
but I'd like to use a 'solar cell' to supply isolated power.

It's too much power for normal photovoltaic isolators by some orders of
magnitude, so I'm considering using one or more photovoltaic cells with
one or more LEDs shining on them. It's all in an enclosure, so there's
no significant ambient light. The cell(s) could be several square
centimeters area. I like this arrangement as the isolation isn't in any
doubt - there could be centimetres of gap.

What sort of size cells would I need for around 30mW? I guess blue LEDs
would be best? An efficiency of 1% (a 3W input) would be fine, even a
bit less. Just musing at the moment and if anyone has any ball-park
feelings or experience that would be good.

Cheers
--
Clive

There are high isolation DC-DC converters out there, not cheap, but ultimately superior to a photvoltaic system.
http://www.mouser.com/search/Refine.aspx?Keyword=164194258&Ns=Pricing%7c0&FS=True&Ntk=P_MarCom

A home-made inductive coupling thing wouldn't be difficult. It could
work through a piece of plexiglas for visible isolation, or just be
traces on opposite sides of a PC board. That could be really cheap in
production.

Or wind a ferrite toroid to make a transformer, and use really well
insulated wire.

But as you say, it's a lot easier to buy an appropriate dc/dc
converter.

For uA of current using a stack of photodiode optocouplers could work,
but for mA inductive coupling is likely the way to go.

The Starbucks near me has those "Powermat" chargers where you stick an
inductor ring to your phone's charging port and lay it on the inductor
ring on the table; I guess they chop the AC up to a high enough freq
that air makes a decent enough core, and a loop only slightly larger
than a quarter can transfer enough energy to charge up a smartphone in
under an hour

Let's spread the rumor that the field will cause warts or insanity or
something.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

Tim Wescott
Guest

Fri Jan 06, 2017 5:25 am

On Thu, 05 Jan 2017 13:42:46 -0800, John Larkin wrote:

Quote:
On Thu, 5 Jan 2017 14:46:04 -0500, bitrex <bitrex_at_de.lete.earthlink.net
wrote:

On 01/05/2017 01:53 PM, John Larkin wrote:
On Thu, 5 Jan 2017 10:24:01 -0800 (PST),
bloggs.fredbloggs.fred_at_gmail.com wrote:

On Thursday, January 5, 2017 at 12:42:48 PM UTC-5, Clive Arthur
wrote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various
solutions, but I'd like to use a 'solar cell' to supply isolated
power.

It's too much power for normal photovoltaic isolators by some orders
of magnitude, so I'm considering using one or more photovoltaic
cells with one or more LEDs shining on them. It's all in an
enclosure, so there's no significant ambient light. The cell(s)
could be several square centimeters area. I like this arrangement
as the isolation isn't in any doubt - there could be centimetres of
gap.

What sort of size cells would I need for around 30mW? I guess blue
LEDs would be best? An efficiency of 1% (a 3W input) would be fine,
even a bit less. Just musing at the moment and if anyone has any
ball-park feelings or experience that would be good.

Cheers --
Clive

There are high isolation DC-DC converters out there, not cheap, but
ultimately superior to a photvoltaic system.
http://www.mouser.com/search/Refine.aspx?Keyword=164194258&Ns=Pricing
%7c0&FS=True&Ntk=P_MarCom

A home-made inductive coupling thing wouldn't be difficult. It could
work through a piece of plexiglas for visible isolation, or just be
traces on opposite sides of a PC board. That could be really cheap in
production.

Or wind a ferrite toroid to make a transformer, and use really well
insulated wire.

But as you say, it's a lot easier to buy an appropriate dc/dc
converter.

For uA of current using a stack of photodiode optocouplers could work,
but for mA inductive coupling is likely the way to go.

The Starbucks near me has those "Powermat" chargers where you stick an
inductor ring to your phone's charging port and lay it on the inductor
ring on the table; I guess they chop the AC up to a high enough freq
that air makes a decent enough core, and a loop only slightly larger
than a quarter can transfer enough energy to charge up a smartphone in
under an hour

Let's spread the rumor that the field will cause warts or insanity or
something.

Whut? Cell phone charging stations cause warts that lead to insanity?

OMG! Get 'em out of the Bay area!!!

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

Jim Thompson
Guest

Fri Jan 06, 2017 5:44 am

On Thu, 05 Jan 2017 16:25:29 -0600, Tim Wescott
<seemywebsite_at_myfooter.really> wrote:

Quote:
On Thu, 05 Jan 2017 13:42:46 -0800, John Larkin wrote:

On Thu, 5 Jan 2017 14:46:04 -0500, bitrex <bitrex_at_de.lete.earthlink.net
wrote:

On 01/05/2017 01:53 PM, John Larkin wrote:
On Thu, 5 Jan 2017 10:24:01 -0800 (PST),
bloggs.fredbloggs.fred_at_gmail.com wrote:

On Thursday, January 5, 2017 at 12:42:48 PM UTC-5, Clive Arthur
wrote:
I want to run a microcontroller circuit at about 3V 10mA on the high
side of a several kilovolt supply. I know there are various
solutions, but I'd like to use a 'solar cell' to supply isolated
power.

It's too much power for normal photovoltaic isolators by some orders
of magnitude, so I'm considering using one or more photovoltaic
cells with one or more LEDs shining on them. It's all in an
enclosure, so there's no significant ambient light. The cell(s)
could be several square centimeters area. I like this arrangement
as the isolation isn't in any doubt - there could be centimetres of
gap.

What sort of size cells would I need for around 30mW? I guess blue
LEDs would be best? An efficiency of 1% (a 3W input) would be fine,
even a bit less. Just musing at the moment and if anyone has any
ball-park feelings or experience that would be good.

Cheers --
Clive

There are high isolation DC-DC converters out there, not cheap, but
ultimately superior to a photvoltaic system.
http://www.mouser.com/search/Refine.aspx?Keyword=164194258&Ns=Pricing
%7c0&FS=True&Ntk=P_MarCom

A home-made inductive coupling thing wouldn't be difficult. It could
work through a piece of plexiglas for visible isolation, or just be
traces on opposite sides of a PC board. That could be really cheap in
production.

Or wind a ferrite toroid to make a transformer, and use really well
insulated wire.

But as you say, it's a lot easier to buy an appropriate dc/dc
converter.

For uA of current using a stack of photodiode optocouplers could work,
but for mA inductive coupling is likely the way to go.

The Starbucks near me has those "Powermat" chargers where you stick an
inductor ring to your phone's charging port and lay it on the inductor
ring on the table; I guess they chop the AC up to a high enough freq
that air makes a decent enough core, and a loop only slightly larger
than a quarter can transfer enough energy to charge up a smartphone in
under an hour

Let's spread the rumor that the field will cause warts or insanity or
something.

Whut? Cell phone charging stations cause warts that lead to insanity?

OMG! Get 'em out of the Bay area!!!

Sno-o-o-ort >:-}

...Jim Thompson
--
| James E.Thompson | mens |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Political correctness and despotism go hand-in-hand.

Political correctness is just another word for control.

As Voltaire said, "To learn who rules over you, simply find out
who you are not allowed to criticize."

Goto page 1, 2  Next

elektroda.net NewsGroups Forum Index - Electronics Design - Photovoltaic isolator