Resistor for neon indicator lamp

[George Herold]

I've got a tankless electric water heater from eemax. that stopped
working the other day. eemax won't provide any component level
support, but I've ordered a new board for $45.00.

When I opened up the unit, after switching off the circuit breaker on
the 240V AC line, I observed that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit. The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color. The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question. Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC? (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like. (Is the
one shown here OK?)

http://en.wikipedia.org/wiki/Neon_lamp

Thanks for any advice.

George H.

 

[Gareth]

On 01/03/2010 21:53, George Herold wrote:

rved that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit. The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color. The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question. Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC? (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like. (Is the
one shown here OK?)

100 ohms is much too small. It's more likely to be 100 k ohms or even
higher.

--
-----------------------------------------------------------------------
To reply to me directly:

Replace privacy.net with: totalise DOT co DOT uk and replace me with
gareth.harris

 

[Jon Kirwan]

On Mon, 1 Mar 2010 13:53:13 -0800 (PST), George Herold
<ggherold@gmail.com> wrote:

I've got a tankless electric water heater from eemax. that stopped
working the other day. eemax won't provide any component level
support, but I've ordered a new board for $45.00.

When I opened up the unit, after switching off the circuit breaker on
the 240V AC line, I observed that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit. The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color. The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question. Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC? (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like. (Is the
one shown here OK?)

http://en.wikipedia.org/wiki/Neon_lamp

Thanks for any advice.

George H.

Assuming the neon bulb is still okay, why not measure the
break down? I'd start with perhaps 100k with your 240V. If
the breakdown is around 100V, the current will be in the area
of 1mA, which is probably safe enough. And 100mW, or so, so
you won't burn something up.

At say 2 watts, you would be talking in the area of 10k, my
guess. Not 100 ohms.

Jon

 

[William Sommerwerck]

Is 100 ohms a good value as a current-limiting resistor
for a small neon lamp running off 240V AC?

It is, if you want the neon lamp to light up whitish purple for less than an
second, then explode.

You need something more in the range of 150K to 200K, possibly even larger.

 

On Mon, 1 Mar 2010 13:53:13 -0800 (PST), George Herold
<ggherold@gmail.com>wrote:

I've got a tankless electric water heater from eemax. that stopped
working the other day. eemax won't provide any component level
support, but I've ordered a new board for $45.00.

When I opened up the unit, after switching off the circuit breaker on
the 240V AC line, I observed that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit. The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color. The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question. Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC? (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like. (Is the
one shown here OK?)

http://en.wikipedia.org/wiki/Neon_lamp

Thanks for any advice.

George H.

An NE2 needs a 22k dropper for 120 volts, do the math.

 

[D Yuniskis]

George Herold wrote:

I've got a tankless electric water heater from eemax. that stopped
working the other day. eemax won't provide any component level
support, but I've ordered a new board for $45.00.

When I opened up the unit, after switching off the circuit breaker on
the 240V AC line, I observed that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit. The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color. The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question. Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC? (60 Hz if that matters.)

Yikes! You should be looking at more like 1mA through the lamp.
Are you sure about the connections in the circuit?

I'm not sure what the I-V curve for the lamp will look like. (Is the
one shown here OK?)

http://en.wikipedia.org/wiki/Neon_lamp

 

[jfeng@my-deja.com]

On Mar 1, 1:53 pm, George Herold <ggher...@gmail.com> wrote:

My question.  Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC?  (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like.  (Is the
one shown here OK?)
Does yours look like the one in the wiki article? If so, I would vote

for a value between 100K and 470K. At 100K, a half-watt resistor
would be marginal, and I would go for one rated for 1 watt. Within
this range, the value is probably not too critical.

 

[George Herold]

On Mar 1, 5:04 pm, "jf...@my-deja.com" <jf...@my-deja.com> wrote:

On Mar 1, 1:53 pm, George Herold <ggher...@gmail.com> wrote:> My question.  Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC?  (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like.  (Is the
one shown here OK?)

Does yours look like the one in the wiki article?  If so, I would vote
for a value between 100K and 470K.  At 100K, a half-watt resistor
would be marginal, and I would go for one rated for 1 watt.  Within
this range, the value is probably not too critical.

Yes the lamp looks like the picture in the wiki article. If I
believe the curve there, then I've got something like 160-200 volts
across the lamp at 20mA. So I've got (call it) 80 V to drop on the
resistor at 20mA.. I get 3 k ohm at a watt or two. Hmm maybe what
looks like brown black brown is a discolored red black red. (I always
have hated the way red and brown look almost the same on the pale blue
body of the metal film resistors.)

100k seems like it won't allow enough current through to keep the lmap
lite. (But I've never worked with neon lamps.)

George H.

 

[George Herold]

On Mar 1, 5:06 pm, Gareth <m...@privacy.net> wrote:

On 01/03/2010 21:53, George Herold wrote:

rved that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit.  The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color.  The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question.  Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC?  (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like.  (Is the
one shown here OK?)

100 ohms is much too small.  It's more likely to be 100 k ohms or even
higher.

--
-----------------------------------------------------------------------
To reply to me directly:

Replace privacy.net with: totalise DOT co DOT uk and replace me with
gareth.harris

Thanks, I'm beginning to think I should just leave it alone and wait
for the replacement PCB. Now sense 'frying' someting else.

George H.

 

[George Herold]

On Mar 1, 5:11 pm, Jon Kirwan <j...@infinitefactors.org> wrote:

On Mon, 1 Mar 2010 13:53:13 -0800 (PST), George Herold





ggher...@gmail.com> wrote:
I've got a tankless electric water heater from eemax. that stopped
working the other day.  eemax won't provide any component level
support, but I've ordered a new board for $45.00.

When I opened up the unit, after switching off the circuit breaker on
the 240V AC line, I observed that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit.  The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color.  The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question.  Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC?  (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like.  (Is the
one shown here OK?)

http://en.wikipedia.org/wiki/Neon_lamp

Thanks for any advice.

George H.

Assuming the neon bulb is still okay, why not measure the
break down?  I'd start with perhaps 100k with your 240V.  If
the breakdown is around 100V, the current will be in the area
of 1mA, which is probably safe enough.  And 100mW, or so, so
you won't burn something up.

At say 2 watts, you would be talking in the area of 10k, my
guess.  Not 100 ohms.

Jon- Hide quoted text -

- Show quoted text -

Thanks Jon. This value seemed way to small to me too.

George H.

 

[George Herold]

On Mar 1, 5:23 pm, D Yuniskis <not.going.to...@seen.com> wrote:

George Herold wrote:
I've got a tankless electric water heater from eemax. that stopped
working the other day.  eemax won't provide any component level
support, but I've ordered a new board for $45.00.

When I opened up the unit, after switching off the circuit breaker on
the 240V AC line, I observed that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit.  The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color.  The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question.  Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC?  (60 Hz if that matters.)

Yikes!  You should be looking at more like 1mA through the lamp.
Are you sure about the connections in the circuit?



I'm not sure what the I-V curve for the lamp will look like.  (Is the
one shown here OK?)

http://en.wikipedia.org/wiki/Neon_lamp- Hide quoted text -

- Show quoted text -

Well I can see that the big (3 to 5 watt) resistor feds the neon
lamp. I don't know what else the circuit does.... I didn't bother to
try and trace the whole thing out. Perhaps I can look at it more
closely tonight and see if I can make something more out of it.

Thanks,

George H.

 

[George Herold]

On Mar 1, 5:21 pm, Meat Plow wrote:

On Mon, 1 Mar 2010 13:53:13 -0800 (PST), George Herold
ggher...@gmail.com>wrote:





I've got a tankless electric water heater from eemax. that stopped
working the other day.  eemax won't provide any component level
support, but I've ordered a new board for $45.00.

When I opened up the unit, after switching off the circuit breaker on
the 240V AC line, I observed that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit.  The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color.  The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question.  Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC?  (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like.  (Is the
one shown here OK?)

http://en.wikipedia.org/wiki/Neon_lamp

Thanks for any advice.

George H.

An NE2 needs a 22k dropper for 120 volts, do the math.- Hide quoted text -

- Show quoted text -

Thanks I'll look up an NE2 and see what I can make out of it.


George H.

 

[Don Klipstein]

In <ef993f27-eac5-404c-a3f8-2d1224188242@j27g2000yqn.googlegroups.com>,
George Herold wrote:

On Mar 1, 5:04 pm, "jf...@my-deja.com" <jf...@my-deja.com> wrote:
On Mar 1, 1:53 pm, George Herold <ggher...@gmail.com> wrote:> My question.
 Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC?  (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like.  (Is the
one shown here OK?)

Does yours look like the one in the wiki article?  If so, I would vote
for a value between 100K and 470K.  At 100K, a half-watt resistor
would be marginal, and I would go for one rated for 1 watt.  Within
this range, the value is probably not too critical.

Yes the lamp looks like the picture in the wiki article. If I
believe the curve there, then I've got something like 160-200 volts
across the lamp at 20mA. So I've got (call it) 80 V to drop on the
resistor at 20mA.. I get 3 k ohm at a watt or two. Hmm maybe what
looks like brown black brown is a discolored red black red. (I always
have hated the way red and brown look almost the same on the pale blue
body of the metal film resistors.)

100k seems like it won't allow enough current through to keep the lmap
lite. (But I've never worked with neon lamps.)

I don't believe the voltages in that curve in Wiki - I would plan on 70
volts and peak current around 3 milliamps (peak voltage of 240 VAC is
about 340 volts).

If the glass bulb's overall length is 3/4 inch, then the neon lamp is
probably an NE-2H. I would use an 82K or 100K 2-watt resistor for an
NE-2H at 240 volts AC. I would err on the high side (100K) to maximize
life of the lamp. I suspect the toated resistor is a 100K 2 watt whose
yellow band was browned by being toasted.

- Don Klipstein (don@misty.com)

 

[Don Klipstein]

In <hmhe69$7fn$1@news.eternal-september.org>, William Sommerwerck wrote:

Is 100 ohms a good value as a current-limiting resistor
for a small neon lamp running off 240V AC?

It is, if you want the neon lamp to light up whitish purple for less than an
second, then explode.

You need something more in the range of 150K to 200K, possibly even larger.

100 ohms in series with a neon lamp at 240 volts AC: Not that I would
try this for the answer, but I suspect both the neon lamp and the resistor
will likely be severely damaged. Either or both may explode, and the neon
lamp may implode.

- Don Klipstein (don@misty.com)

 

[Jamie]

George Herold wrote:

I've got a tankless electric water heater from eemax. that stopped
working the other day. eemax won't provide any component level
support, but I've ordered a new board for $45.00.

When I opened up the unit, after switching off the circuit breaker on
the 240V AC line, I observed that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit. The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color. The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question. Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC? (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like. (Is the
one shown here OK?)

http://en.wikipedia.org/wiki/Neon_lamp

Thanks for any advice.

George H.

100K would me more like it.. "100,000"

 

[John Larkin]

On Mon, 1 Mar 2010 13:53:13 -0800 (PST), George Herold
<ggherold@gmail.com> wrote:

I've got a tankless electric water heater from eemax. that stopped
working the other day. eemax won't provide any component level
support, but I've ordered a new board for $45.00.

When I opened up the unit, after switching off the circuit breaker on
the 240V AC line, I observed that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit. The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color. The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question. Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC? (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like. (Is the
one shown here OK?)

http://en.wikipedia.org/wiki/Neon_lamp

Thanks for any advice.

George H.

Numbers more like 330K to 560K are more reasonable. Higher currents
will sputter the gas and make the thing fail sooner.

Better yet, use an LED.

John

 

[George Herold]

On Mar 1, 5:48 pm, d...@manx.misty.com (Don Klipstein) wrote:

In <ef993f27-eac5-404c-a3f8-2d1224188...@j27g2000yqn.googlegroups.com>,





George Herold wrote:
On Mar 1, 5:04 pm, "jf...@my-deja.com" <jf...@my-deja.com> wrote:
On Mar 1, 1:53 pm, George Herold <ggher...@gmail.com> wrote:> My question.
Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC? (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like. (Is the
one shown here OK?)

Does yours look like the one in the wiki article? If so, I would vote
for a value between 100K and 470K. At 100K, a half-watt resistor
would be marginal, and I would go for one rated for 1 watt. Within
this range, the value is probably not too critical.

Yes the lamp looks like the picture in the wiki article.   If I
believe the curve there, then I've got something like 160-200 volts
across the lamp at 20mA.  So I've got (call it) 80 V to drop on the
resistor at 20mA.. I get 3 k ohm at a watt or two.  Hmm maybe what
looks like brown black brown is a discolored red black red.  (I always
have hated the way red and brown look almost the same on the pale blue
body of the metal film resistors.)

100k seems like it won't allow enough current through to keep the lmap
lite.  (But I've never worked with neon lamps.)

  I don't believe the voltages in that curve in Wiki - I would plan on 70
volts and peak current around 3 milliamps (peak voltage of 240 VAC is
about 340 volts).

  If the glass bulb's overall length is 3/4 inch, then the neon lamp is
probably an NE-2H. I would use an 82K or 100K 2-watt resistor for an
NE-2H at 240 volts AC. I would err on the high side (100K) to maximize
life of the lamp.  I suspect the toated resistor is a 100K 2 watt whose
yellow band was browned by being toasted.

 - Don Klipstein (d...@misty.com)- Hide quoted text -

- Show quoted text -

Excellent, Thanks Don. I like the faded yellow stripe idea. The bulb
is about 1/2 that size. It's standing straight up and the tip of the
glass is 0.4" (10mm) above the circuit board.

George H.

 

[George Herold]

On Mar 1, 7:32 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:

On Mon, 1 Mar 2010 13:53:13 -0800 (PST), George Herold





ggher...@gmail.com> wrote:
I've got a tankless electric water heater from eemax. that stopped
working the other day.  eemax won't provide any component level
support, but I've ordered a new board for $45.00.

When I opened up the unit, after switching off the circuit breaker on
the 240V AC line, I observed that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit.  The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color.  The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question.  Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC?  (60 Hz if that matters.)
I'm not sure what the I-V curve for the lamp will look like.  (Is the
one shown here OK?)

http://en.wikipedia.org/wiki/Neon_lamp

Thanks for any advice.

George H.

Numbers more like 330K to 560K are more reasonable. Higher currents
will sputter the gas and make the thing fail sooner.

Better yet, use an LED.

John- Hide quoted text -

- Show quoted text -

Well somehow this must also feed power to some other part of the
circuit. There's also an LM324 and small triac Q601e3 on the pcb.

George H.

 

[Don Klipstein]

In <759684f3-b852-4ed1-9333-a5522fc8ad6c@g19g2000yqe.googlegroups.com>,
George Herold wrote:

On Mar 1, 5:48 pm, d...@manx.misty.com (Don Klipstein) wrote:
In <ef993f27-eac5-404c-a3f8-2d1224188...@j27g2000yqn.googlegroups.com>,
George Herold wrote:

<SNIP to here>

Yes the lamp looks like the picture in the wiki article.   If I
believe the curve there, then I've got something like 160-200 volts
across the lamp at 20mA.  So I've got (call it) 80 V to drop on the
resistor at 20mA.. I get 3 k ohm at a watt or two.  Hmm maybe what
looks like brown black brown is a discolored red black red.  (I always
have hated the way red and brown look almost the same on the pale blue
body of the metal film resistors.)

100k seems like it won't allow enough current through to keep the lmap
lite.  (But I've never worked with neon lamps.)

  I don't believe the voltages in that curve in Wiki - I would plan on 70
volts and peak current around 3 milliamps (peak voltage of 240 VAC is
about 340 volts).

  If the glass bulb's overall length is 3/4 inch, then the neon lamp is
probably an NE-2H. I would use an 82K or 100K 2-watt resistor for an
NE-2H at 240 volts AC. I would err on the high side (100K) to maximize
life of the lamp.  I suspect the toated resistor is a 100K 2 watt whose
yellow band was browned by being toasted.

Excellent, Thanks Don. I like the faded yellow stripe idea. The bulb
is about 1/2 that size. It's standing straight up and the tip of the
glass is 0.4" (10mm) above the circuit board.

That sounds just a little small for the A1B (mini NE-2) and the A1C
(mini NE-2H), so I suspect your lamp is one of those. Given the size of
the resistor, I think it's the latter.

If your neon lamp kicked the bucket along with the resistor (more likely
it survived, at least well enough to glow from 240 volts AC), Radio Shack
may still carry these (a litle incorrectly calling them NE-2H).

- Don Klipstein (don@misty.com)

 

[John Fields]

On Mon, 1 Mar 2010 13:53:13 -0800 (PST), George Herold
<ggherold@gmail.com> wrote:

I've got a tankless electric water heater from eemax. that stopped
working the other day. eemax won't provide any component level
support, but I've ordered a new board for $45.00.

When I opened up the unit, after switching off the circuit breaker on
the 240V AC line, I observed that a big (maybe 3-5 watt) (metal film?)
resistor was discolored and was an open circuit. The markings look
like 100 ohms, but because of the discoloration it's hard to be sure.
I say metal film because the resistor is pale blue in color. The
resistor feds a neon indicator bulb... (And probablly more of the
circuitry.)

My question. Is 100 ohms a good value as a current limiting resistor
for a small neon lamp running off 240 V AC?

---
No.

For a small neon lamp like an NE-2, (GE 3AD) with a recommended current
of 0.3mA and a nominal holding voltage of about 60V, peak, that's about
42VRMS, so the resistor would have to drop about 200V at 300ľA:

Vs - Vne 200V
R = ---------- ~ ------- ~ 670k oms
Ine 3e-4A

and it would dissipate:

P = IE = 3e-4A * 200V ~ 0.06 watts

If that resistor were 100 ohms, then with 200V dropped across it
there'd be 200 amperes through it _and_ the neon lamp, which they'd both
hate for a little while.

OTOH, if the resistor is 100k it'll drop about 200V with a neon lamp in
series, which will let about 2mA through when the lamp fires.

That'll cause the resistor to dissipate about 0.4 watts, which doesn't
explain why it got toasted, since even into a short it would only
dissipate about:


E˛ 240˛V
P = --- = ------- = 0.576 watts
R 1e5R

Just for grins, let's say it's a 3 watt resistor running full bore in
series with a load (like a high current neon lamp) drawing 5mA.

Then the value of the resistor would be:

E˛ 200˛V
R = --- = ------- = 13,333 ohms ~ 13k
P 3W

and if there was some circuitry downstream from the lamp, which shorted,
then the resistor would dissipate:

E˛ 240˛V
P = --- = ------- = 4.43 watts
R 13e3R

Not huge but, anyway, without a schematic it's all just conjecture.
---

(60 Hz if that matters.)

I'm not sure what the I-V curve for the lamp will look like. (Is the
one shown here OK?)

http://en.wikipedia.org/wiki/Neon_lamp

---
Only in a very general way; here's a much better one for your
application:

d7iqo5lphgp0k15o8fh2ccal5eoi0c29h0@4ax.com

JF