Wire size in power supply important

[DrPhoxinus]

85CCB93C-6A80-48EB-A206-C7A9E7EDCD06.png (107.51 KiB) Viewed 4862 times

Received an Ortholux I for Christmas from my wonderful wife.

Couldn’t wait to light it up.

Connected to a favorite power supply adjustable 3v-12v at 5A, 110-240 VAC for under $20 at Amazon.

Ordered female connectors 5.5 mm x2.1 mm from several vendors.

I was delighted when the scope light up with its 8110 bulb, 6v at 5 amps

Within minutes the female connector cable was too hot to touched. I measured the conductor at 0.3 mm, probably 28 AWG. That size is rated at 1.4 amps.

Measured another connector which was 0.7 mm
probably 20 gauge.

Just ordered females from eBay with 18 gauge wire, rated at 5 amps.

Wire size matters

[jfiresto]

Did either vendor give a maximum rating for their pigtailed power connectors?

I looked again at the specs for some 5.5/2.1mm male-female extension cables I bought in 2020 to power a couple mirrorless cameras. Translated they read: "recommended for up to 36VDC and 3A maximum load or less". A camera will not overheat that, but if the cable is too thin, the voltage will plummet as the shutter fires and disturb the camera.

The deciding issue for me was a cable's flexibility: some were annoyingly stiff.

[DrPhoxinus]

Except for the order rated at 5 amps which I have yet to receive, there were no ratings. Caveat Emptor

Looking at the wire gauge table your cable is 24 gauge.

[jfiresto]

I reckon they are more toward 0.5mm^2 (20AWG), the limit of what some cage clamp connectors will accept. Probably midway or 22AWG. The DC connectors also have a current limit. The first five I looked at have a 1A or 2A rating.

Well, now that you have got me whipped into a researching frenzy, from surveying some Meanwell power supplies it looks like the beefiest 5.5/2.1mm plug/socket can carry somewhat more than 6A.

[DrPhoxinus]

I changed my AO series 10 halogens from 6v to 12v and that reduced amps from 3 to 1.5 so conductor size was less important. Besides 12volt bulbs are pretty cheap.

[smollerthings]

Anybody knows why most of the bulbs on the microscopes were 6v? This leads to huge currents to manage. What was the advantage?

[Leitzcycler]

I don't know about microscopes for sure. But my grey Ferguson tractor (1949) has also 6V system. Maybe it was more common in ancient times and has some historical background.

Happy New Year!

[PeteM]

Anybody knows why most of the bulbs on the microscopes were 6v? This leads to huge currents to manage. What was the advantage?

Used to be 15 to 20 watts was pretty typical for the scopes with tungsten or tungsten halogen bulbs. 6v made sense for that. As one 1980-ish example, Olympus used 6v bulbs for their 20 watt BH2 scopes and 12v bulbs for their 100 watt BH2/BHS scopes.

[smollerthings]

20/6 is still 3.3A and I suppose 220->6v takes more coils than 220->12v. There must be an advantage I am not seeing.

Happy holidays everyone!

[Alexander]

... I suppose 220->6v takes more coils than 220->12v. There must be an advantage I am not seeing.

It depends on perspective. With a fixed number of coils on the primary side of the transformer you less coils on the secondary for 6V. With a fixed number of coils on the secondary side you need more coils on the primary.

The real reason may have been color temperature. A 6V 5A bulb runs hotter than a 12V 2.5A one and produces a more pleasing color temperature. The expensive transformers and lighthouses from these days handled the high currents well. Remember that a black Ortholux was priced in the range of a Mercedes car.

Do you have the blue CB12-filter for the lighthouse? It produces day-light color temperature with the Osram 8110.

[DrPhoxinus]

Yes,

There is a blue filter where the field iris should be and it makes a big difference.

As to the 6v /12v thing, I was talking about the 6v 20 watt halogen bulb in the AO Series 10. Going to. 12 volts cuts the amps in half for the same wattage for the scope.

So the conductor heating wasn’t so problematic as powering a 8110 at 5 amps.

When the new heavier pigtails come in I am going to experiment with using a PWM at 6 volts, keeping the voltage at 6v but slicing the duty cycle

[Alexander]

Yes,

There is a blue filter where the field iris should be and it makes a big difference.

The field iris is build into the Berek condenser. Hope you find the information how to service it. Unfortunately I cannot help with this. The Berek is a very fine condenser. Much better than anything sold today.

[ker2x]

Electrician here,

Don't wait for it to be too hot to touch to change it. Even if it's warm : change it.
Beware of the connector too.

I may be stating the obvious but :
- Amp affect the conductor size
- voltage affect the insulator size

[Greg Howald]

Everything regarding electronics keeps getting smaller, requiring less voltage and less amperage. I'm afraid the days of halogen and tungsten lighting are going away, making it more difficult to acquire higher quality equipment like what you have found you need. Geez... When I got my degree in electronics engineering 50 years ago we were using vacuum tubes, and such a rare thing as a punch card reading computer was the size of a small house. Aahh. Those were the days. It was a maze but you could see what you were doing. Last month I bought a pretty good refurbished computer for forty bucks.
Regarding microscopy, 6 volts was the standard in early days. Everything seemed to run on 6 volts. Your car. Your portable radio. Marine equipment. Lighting. All were 6 volt. As battery technology increased the whole world went to 12 volt almost over night, and it is still the standard.
The difference between the two in microscopy may well be the color spectrum produced by the element. One bulb may be more of a red spectrum than the other. For us, finding those comparative specifications may be a difficult challenge.

[DrPhoxinus]

I got my first ham radio a mere 53 years ago.
The Europeans called vacuum tubes valves, which is truer to their functioning given grids.

Technical art moves on. The tungsten filament is over 5000 F
wasting a lot of power.

I like halogens. Control with a PWM doesn’t have the flicker issues like LEDs.

First try with a PWM at 6 v didn’t work. Device is labeled 12-24 VDC.

Still, the old stuff is fun

[jfiresto]

... I like halogens. Control with a PWM doesn’t have the flicker issues like LEDs....

It can if the PWM frequency is too low (e.g., 100/120hz) and you choose an unfortunate exposure time when taking stills or shooting video. To avoid flicker, the Schott 150W halogen light source next to me, rectifies and filters the house/mains voltage to a steady DC and then modulates it at 20khz.

[EYE C U]

https://www.bluesea.com/support/article ... DC_Circuit