Voltage halver.

[p***@easthope.ca]

A variable power adapter is required to drive a 6 V, 30 W incandescent
bulb in a microscope.

Similar to the 3-12 V 5 A adapter here.
https://www.ebay.ca/itm/305207182573
An adapter providing 1.5-6 V output would be better but I haven't
found one.

Rather than limit the adjustment to 6 V, I think of halving the
output. An integrated circuit in a 4 port package is conceivable.

Does the marketplace offer a solution?
Another idea?

Thanks, ... P.

[Roger Hayter]

Post by p***@easthope.ca
A variable power adapter is required to drive a 6 V, 30 W incandescent
bulb in a microscope.
Similar to the 3-12 V 5 A adapter here.
https://www.ebay.ca/itm/305207182573
An adapter providing 1.5-6 V output would be better but I haven't
found one.
Rather than limit the adjustment to 6 V, I think of halving the
output. An integrated circuit in a 4 port package is conceivable.
http://youtu.be/VJfqBQ2ybpk
Does the marketplace offer a solution?
Another idea?
Thanks, ... P.

Something like this would do the job, provided you're careful to limit the
voltage you use!

https://www.amazon.co.uk/adjustable-switching-precision-charging-interface/dp/B09C8MT4KM?th=1


This is a cheap variable bench power supply which will supply 5A at 6V. You
may want to look at your local market for a suitable mains voltage and plug,
and there are a lot of makes.

Otherwise, AFAICS you're going to need a somewhat more than 6V 5A power supply
and a separate variable voltage converter, which won't be much less in price,
and may need a box to put it in for electrical neatness.


BTW, my memory of incandescent bulbs is that at 1.5 volts a 6V bulb will
barely glow a dim red, BICBW.

[Liz Tuddenham]

Post by p***@easthope.ca
A variable power adapter is required to drive a 6 V, 30 W incandescent
bulb in a microscope.
Similar to the 3-12 V 5 A adapter here.
https://www.ebay.ca/itm/305207182573
An adapter providing 1.5-6 V output would be better but I haven't
found one.
Rather than limit the adjustment to 6 V, I think of halving the
output. An integrated circuit in a 4 port package is conceivable.
http://youtu.be/VJfqBQ2ybpk
Does the marketplace offer a solution?
Another idea?

A 6v transformer and an adjustable resistor made from an old electric
fire bar and two jubilee clips?

[Roger Hayter]

Post by Liz Tuddenham

Post by p***@easthope.ca
A variable power adapter is required to drive a 6 V, 30 W incandescent
bulb in a microscope.
Similar to the 3-12 V 5 A adapter here.
https://www.ebay.ca/itm/305207182573
An adapter providing 1.5-6 V output would be better but I haven't
found one.
Rather than limit the adjustment to 6 V, I think of halving the
output. An integrated circuit in a 4 port package is conceivable.
http://youtu.be/VJfqBQ2ybpk
Does the marketplace offer a solution?
Another idea?

A 6v transformer and an adjustable resistor made from an old electric
fire bar and two jubilee clips?

I thought of that, but it is not very useful to adjust while looking down the
microscope and I wondered if AC might affect microphotography. Have you seen
the price of 30W WW pots or "rheostats"?

[Roger Hayter]

Post by Roger Hayter

Post by Liz Tuddenham

Post by p***@easthope.ca
A variable power adapter is required to drive a 6 V, 30 W incandescent
bulb in a microscope.
Similar to the 3-12 V 5 A adapter here.
https://www.ebay.ca/itm/305207182573
An adapter providing 1.5-6 V output would be better but I haven't
found one.
Rather than limit the adjustment to 6 V, I think of halving the
output. An integrated circuit in a 4 port package is conceivable.
http://youtu.be/VJfqBQ2ybpk
Does the marketplace offer a solution?
Another idea?

A 6v transformer and an adjustable resistor made from an old electric
fire bar and two jubilee clips?

I thought of that, but it is not very useful to adjust while looking down the
microscope and I wondered if AC might affect microphotography. Have you seen
the price of 30W WW pots or "rheostats"?

Also, an electric fire element is going to be about 30ohms in North America,
and since you want fractions of 2ohms adjustment over 1 to 3 turns is going to
be somewhat fiddly.

[Liz Tuddenham]

Post by Roger Hayter

Post by Liz Tuddenham

Post by p***@easthope.ca
A variable power adapter is required to drive a 6 V, 30 W incandescent
bulb in a microscope.
Similar to the 3-12 V 5 A adapter here.
https://www.ebay.ca/itm/305207182573
An adapter providing 1.5-6 V output would be better but I haven't
found one.
Rather than limit the adjustment to 6 V, I think of halving the
output. An integrated circuit in a 4 port package is conceivable.
http://youtu.be/VJfqBQ2ybpk
Does the marketplace offer a solution?
Another idea?

A 6v transformer and an adjustable resistor made from an old electric
fire bar and two jubilee clips?

I thought of that, but it is not very useful to adjust while looking down the
microscope and I wondered if AC might affect microphotography. Have you seen
the price of 30W WW pots or "rheostats"?

I hadn't, but I expect they would be expensive.. By comparison, making
big power resistors is surprisingly cheap -- I had to make some for a
5kW organ blower starter, so I had some slate bars cut for me by a
monumental mason and wound them by hand (with tappings). The total
cost was surprisingly low.

I don't see how AC wold be a problem with microphotography unless you
were worried about ripple in the light output. Low voltage lamps like
that heve a short thick filament with high thermal inertia, so they were
often used as the exciter lamp for for sound film reproduction. Any
ripple would have generated a 100c/s hum, but there has been very little
sign of that on the vintage projectors I have worked on.

[p***@easthope.ca]

Post by Roger Hayter
I thought of that, but it is not very useful to adjust while looking down the
microscope and I wondered if AC might affect microphotography. Have you seen
the price of 30W WW pots or "rheostats"?

Certainly adjustment while looking down the scope must be convenient.

Input voltage is another factor I should have mentioned. The scope is
going to Africa where the wall socket will probably be 220 V. The 3-12 V
adapter I have accepts 110-240 V input. Good.

6 V is roughly the bottom 1/8 th of the range of the adapter. Halving
the output with efficient switching would allow use of the full range
of adjustment.

I was hoping someone would cite a voltage halver as simple as this.
https://www.ebay.ca/itm/404142157480

Soldering leads to an IC would be a reasonable 2nd possibility.

Thx, ... P.

[Chris Jones]

Post by p***@easthope.ca
A variable power adapter is required to drive a 6 V, 30 W incandescent
bulb in a microscope.
Similar to the 3-12 V 5 A adapter here.
https://www.ebay.ca/itm/305207182573
An adapter providing 1.5-6 V output would be better but I haven't
found one.
Rather than limit the adjustment to 6 V, I think of halving the
output. An integrated circuit in a 4 port package is conceivable.
http://youtu.be/VJfqBQ2ybpk
Does the marketplace offer a solution?
Another idea?
Thanks, ... P.

If you connect two identical bulbs in series, then the voltage across
each will be half of the supply voltage. So, connect another identical
bulb in series. You won't find a simpler circuit!

[p***@easthope.ca]

Hello Chris,

Post by Chris Jones
If you connect two identical bulbs in series, then the voltage across
each will be half of the supply voltage. So, connect another identical
bulb in series. You won't find a simpler circuit!

Understood. Thanks. No spare bulb handy but can put a resistor in
series with the bulb.

Switched voltage halving would be more efficient.

A 6 V, 5 A adapter similar to eBay 305207182573 would be even better
but I haven't found one.

Thanks, ... P.

[Ralph Mowery]

Post by p***@easthope.ca
Understood. Thanks. No spare bulb handy but can put a resistor in
series with the bulb.
Switched voltage halving would be more efficient.

Put a few diodes in series. More diodes and less voltage of about .5 to
.7 volts per diode.

[legg]

Post by p***@easthope.ca
A variable power adapter is required to drive a 6 V, 30 W incandescent
bulb in a microscope.
Similar to the 3-12 V 5 A adapter here.
https://www.ebay.ca/itm/305207182573
An adapter providing 1.5-6 V output would be better but I haven't
found one.
Rather than limit the adjustment to 6 V, I think of halving the
output. An integrated circuit in a 4 port package is conceivable.
http://youtu.be/VJfqBQ2ybpk
Does the marketplace offer a solution?
Another idea?
Thanks, ... P.

What does the microscope manufacturer supply for this function?

If you have a >6V source, simple 555-type buck regulators are
available with minimum output listed as 1.8V

https://www.aliexpress.com/item/1005006482720286.html?

These generally regulate the negative output terminal, unfiltered.
This would not be an issue for an isolated 6V incandescent lamp.

Rl

[p***@easthope.ca]

Post by legg
What does the microscope manufacturer supply for this function?

The scope is a Zeiss OPMI 1. Google finds many listings of various
models with various power supplies.

This scope was donated without the power supply; I can't say what the
original supply was but Zeiss built nice equipment capable of
continuous and reliable duty.

Post by legg
If you have a >6V source, simple 555-type buck regulators are
available with minimum output listed as 1.8V
https://www.aliexpress.com/item/1005006482720286.html?
These generally regulate the negative output terminal, unfiltered.
This would not be an issue for an isolated 6V incandescent lamp.

Good idea. Will see what Lee's Electronics has in stock. I expect to
have to limit the voltage somehow to prevent burning the bulb.

Thanks, ... P.

[legg]

Post by p***@easthope.ca

Post by legg
What does the microscope manufacturer supply for this function?

The scope is a Zeiss OPMI 1. Google finds many listings of various
models with various power supplies.
This scope was donated without the power supply; I can't say what the
original supply was but Zeiss built nice equipment capable of
continuous and reliable duty.

Post by legg
If you have a >6V source, simple 555-type buck regulators are
available with minimum output listed as 1.8V
https://www.aliexpress.com/item/1005006482720286.html?
These generally regulate the negative output terminal, unfiltered.
This would not be an issue for an isolated 6V incandescent lamp.

Good idea. Will see what Lee's Electronics has in stock. I expect to
have to limit the voltage somehow to prevent burning the bulb.
Thanks, ... P.

Using a lower voltage wall wart as a source is the easiest limiting
method. Overvolting the bulb by 50% temporarily will not be
catastrophic. If the wall wart is internally limited for power or
current, then overvoltage is unlikely.

There may be issues with wall wart curremt limiting which is best
addressed with filtering (~ capacitive) between the two devices.

The 555 buck regulators are dumb, in themselves, which is often an
advantage driving nonlinear (incandescent) loads. The unit with the
large yellow PTC on-board is a good bet as load protection.

Just remeber that the 'common' rail in the system will be the +rail
of the 555 buck output. The wall wart won't care - neither will
the lamp. You're effectively driving the lamp with a negative supply.

The unfiltered output is a high frequency square wave with peaks
equal to the wall wart's labelled voltage.

Filtering that output to DC would require an external 5A buck diode,
a 5A choke and an electrolytic cap - effectively doubling the size,
weight (and cost) of the regulator section, at no benefit to the lamp.

RL

[legg]

Post by p***@easthope.ca

Post by legg
What does the microscope manufacturer supply for this function?

The scope is a Zeiss OPMI 1. Google finds many listings of various
models with various power supplies.

If you are intending use of this device in it's intended environment,
you should use the mfr's designated power supply, as this is the
major system component that gives it biomedical safety certification.

RL

[legg]

I also note that in the zeiss opmi_1 manual, a 12V 100W halogen lamp
is specified - and a self-resetting thermal limiter is built into
the lamp holder.

RL

[John Keiser]

Post by legg
I also note that in the zeiss opmi_1 manual, a 12V 100W halogen lamp
is specified - and a self-resetting thermal limiter is built into
the lamp holder.
RL

Temu has an enclosed 0-12v LED dimmer for $2.69 that might work with a
wall wart but only "rated" for 8A.

[legg]

Post by John Keiser

Post by legg
I also note that in the zeiss opmi_1 manual, a 12V 100W halogen lamp
is specified - and a self-resetting thermal limiter is built into
the lamp holder.
RL

Temu has an enclosed 0-12v LED dimmer for $2.69 that might work with a
wall wart but only "rated" for 8A.

The zeiss opmi_1 uses a light pipe.

RL

[p***@easthope.ca]

RL and all,

Post by legg
I also note that in the zeiss opmi_1 manual, a 12V 100W halogen lamp
is specified - and a self-resetting thermal limiter is built into
the lamp holder.

You have an original paper manual?

OPMI 1 is a family of microscopes rather than a specific model;
correct?

A search in eBay, for example, finds many variants. Appears that
components were assembled according to requirements of a customer.

A search found this URL.
http://www.frankshospitalworkshop.com/equipment/documents/microscopes/user_manuals/Zeiss%20OPMI%201%20FC%20Surgical%20Microscope%20User%20Manual.pdf

The 2nd supplementary page after page 31 lists these bulbs.

Endure Number Spare Bulbs

90-1200 Zeiss 6V 30W Bt58Z 390158
90-1201 Zeiss 6V 50W Bt86Z 390186
90-1202 Zeiss 12V 100W HLX #64626 380075 1020
90-1203 EFR Housing #900
90-1204 Zeiss 15V 150W EFR 310198
90-1205 Zeiss 12V 100W HLX #64627 380079 9040
90-1206 Zeiss Superlux 40
90-1207 Zeiss Superlux 175
90-1208 Zeiss Superlux 300 with Cartridge
90-1209 Zeiss Superlux 300 Bulb Only - No Housing or Meter

90-1302 ELS 150 21V 150W EKE
90-1400 ELS 250 24V 250W ELC
90-1403 ELS 24 60V 24W Metal Halide
90-1402 ILO 300W with Cartridge

EFR, ELS and ILO are bulb manufacturers?

After my original enquiry, also found a page for a replacement LED
illuminator. 700+ $US. Beyond my budget at present.

Also found some old bulbs in boxes labeled 390153. They have the
unusual (Zeiss?) triangular base and the filament is parallel to the
bulb axis. The 39015 has the filament crosswise to the bulb axis.

Also found an inexpensive motor controller which adjusts light
intensity nicely. The adjustable power brick can be set to deliver 6
V. The controller connected beyond that adjusts intensity.

In case a 90-1202 Zeiss 12V as listed above turns up, my power supply
should suffice for that also.

Thanks to all for the replies, ... P.

[legg]

Post by p***@easthope.ca
RL and all,

Post by legg
I also note that in the zeiss opmi_1 manual, a 12V 100W halogen lamp
is specified - and a self-resetting thermal limiter is built into
the lamp holder.

You have an original paper manual?
OPMI 1 is a family of microscopes rather than a specific model;
correct?
A search in eBay, for example, finds many variants. Appears that
components were assembled according to requirements of a customer.
A search found this URL.
http://www.frankshospitalworkshop.com/equipment/documents/microscopes/user_manuals/Zeiss%20OPMI%201%20FC%20Surgical%20Microscope%20User%20Manual.pdf
The 2nd supplementary page after page 31 lists these bulbs.
Endure Number Spare Bulbs
90-1200 Zeiss 6V 30W Bt58Z 390158
90-1201 Zeiss 6V 50W Bt86Z 390186
90-1202 Zeiss 12V 100W HLX #64626 380075 1020
90-1203 EFR Housing #900
90-1204 Zeiss 15V 150W EFR 310198
90-1205 Zeiss 12V 100W HLX #64627 380079 9040
90-1206 Zeiss Superlux 40
90-1207 Zeiss Superlux 175
90-1208 Zeiss Superlux 300 with Cartridge
90-1209 Zeiss Superlux 300 Bulb Only - No Housing or Meter
90-1302 ELS 150 21V 150W EKE
90-1400 ELS 250 24V 250W ELC
90-1403 ELS 24 60V 24W Metal Halide
90-1402 ILO 300W with Cartridge
EFR, ELS and ILO are bulb manufacturers?
After my original enquiry, also found a page for a replacement LED
illuminator. 700+ $US. Beyond my budget at present.
Also found some old bulbs in boxes labeled 390153. They have the
unusual (Zeiss?) triangular base and the filament is parallel to the
bulb axis. The 39015 has the filament crosswise to the bulb axis.
Also found an inexpensive motor controller which adjusts light
intensity nicely. The adjustable power brick can be set to deliver 6
V. The controller connected beyond that adjusts intensity.
In case a 90-1202 Zeiss 12V as listed above turns up, my power supply
should suffice for that also.
Thanks to all for the replies, ... P.

In the reference I found for zeiss opmi_1, illumination is
delivered to the optics package through a long (1m ?) light
pipe (or possibly bundles of same).

RL