Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Need help with Nernst lamp.

I recently saw one of PhotonicInduction's new yt vids where he displays a Nernst lamp. I was trying to replicate this but need to know at what temperature zirconium dioxide will glow (taken from a ceramic knife), and how much voltage/current will be needed to keep the piece glowing. I tried googling this but came up with vague results.
Thanks In advance -Ray, KD2JID
 

shortbus=

Well-Known Member
Most Helpful Member
How do I know if my knife has yttria in it

Probably doesn't now days. Being mass produced and sold at a low price probably makes it less like to use a kind of obscure chemical. Have you tried Emailing the company that made the knife?
 

shortbus=

Well-Known Member
Most Helpful Member
What is the end game for doing this? Just as an experiment? If you read the Wiki link about the lamp, it says today they are using a silicon carbide bar/rod for the new style lamps. Carbide drills are readily available that may work.

" (Recently, even this has become obsolete as Nernst glowers have been largely replaced for this purpose by silicon carbide glow bars or "globars",[2] which are conductive even at room temperature and therefore need no preheating.) " From - https://en.wikipedia.org/wiki/Nernst_lamp
 

schmitt trigger

Well-Known Member
I also have seen Photonicinduction’s new video.
This kid has progressed from shattering and abusing electronics to a legitimate curator of obscure electronic devices.
Two thumbs up!
 
What is the end game for doing this? Just as an experiment? If you read the Wiki link about the lamp, it says today they are using a silicon carbide bar/rod for the new style lamps. Carbide drills are readily available that may work.

" (Recently, even this has become obsolete as Nernst glowers have been largely replaced for this purpose by silicon carbide glow bars or "globars",[2] which are conductive even at room temperature and therefore need no preheating.) " From - https://en.wikipedia.org/wiki/Nernst_lamp
Yeah just a fun little experiment. I also bought a piece of 8% yytria stabilized zirconia from eBay. On the listing it says it would be a good nernst glower. However I’m having trouble getting it glowing. I surrounded it with a piece of nichrome wire that glows yellow hot. What voltage/temp do I need to make it glow? I’ve tried 30 volts across it at different points with no luck. Do I need to use a higher voltage?
EDIT: here are some specs and a link:

Electrical Resistivity at 20 C: 10¬10 Ohm*cm

Electrical resistance at 600 C: 101 Ohm*cm

Length: 1.325”
LINK: https://www.ebay.com/itm/302398410211
 
Last edited:

rjenkinsgb

Well-Known Member
Most Helpful Member
From the listing:
When metallized with Platinum group metals, the will be great Nerst glowers

So, the seller is not claiming they will work as supplied??
I'm not sure exactly what that means; but I'm guessing it's adding metallic "endcaps" that are chemically bonded in to the material for electrical connectivity.

If you have it around 600'C, the resistance should be extremely low and it should take a relatively high current at 30V, if you have proper contact to the material.
 

Buk

Active Member
Electrical resistance at 600 C: 101 Ohm*cm

Do you have a way of measuring temperature at that level?

If so, you could measure the resistance whilst heating it in a flame.

Those tubes have a cross section of almost exactly 12mm\(^2 \); or 0.12cm\(^2 \)so if you put your (good?) connections 30mm apart and get it to 600C you should see a resistance of ~2k5 Ohms.

30V through 2k5 is 0.0119A; so it would only be generating around 1/3W which is almost certainly not enough to keep it at 600C without continued further external heat, let alone get it there from a lower temp where the resistance would be exponentially higher.
 
Last edited:

rjenkinsgb

Well-Known Member
Most Helpful Member
Ohms*cm * cm^2 area * cm length = Ohms.

At 600'C, 10^1 ohms*cm = 10 Ohms * cm

10 * 0.12 * 3 = 3.6 Ohms

One of us is a very long way out??
 

Buk

Active Member
The one is superscript in the ebay listing

Hm. According to this article, the the bulk resistivity of 3 mol% yttria-stabilized zirconia at 1400°C is 133 ohm*cm.

An order of magnitude lower resistance at < 1/2 the temperature, for 8 mol% doesn't seem likely...

But my caclulation was screwed anyway.
 
From the listing:
When metallized with Platinum group metals, the will be great Nerst glowers

So, the seller is not claiming they will work as supplied??
I'm not sure exactly what that means; but I'm guessing it's adding metallic "endcaps" that are chemically bonded in to the material for electrical connectivity.

If you have it around 600'C, the resistance should be extremely low and it should take a relatively high current at 30V, if you have proper contact to the material.
I asked him and he said to just connect a voltage source and apply heat to the ceramic. How would I know if my connection is bad? I've connected 2 alligator wires to the ends and heated it with nichrome wire, when I measured resistance my meter still says ol. How would I make a good connection to the glower?
 

rjenkinsgb

Well-Known Member
Most Helpful Member
That's likely the problem, you have a few very tiny contact points, so very high resistance.

It needs somehow metallising with something that will not melt or burn off when incandescent. That's presumably why the ebay listing mentions platinum.

I believe there are electroless plating solutions for such as nickel and gold available, one of those may add some kind of conductive surface?

Electroless tin is readily available for PCB work, but the melting point is far too low for that use.
 

Buk

Active Member
How would I make a good connection to the glower?
Same article mentions:
The electric field was applied to the specimen by wrapping fine Pt wire (0.13 mm dia.) around each end of the gage section as shown in Figure 1.

They probably use platinum because of it strength at high temps. Copper is 6x more conductive, so a few turns of fine copper wire should work.

Edit: come to think of it, you mentioned using nichrome wire, that would probably better stand the temps.
 

Latest threads

EE World Online Articles

Loading
Top