Re: [CAD_CAM_EDM_DRO] Re: Two Lamps?

On Dec 14, 2004, at 11:43 PM, Torsten wrote:

>
> Some body suggested using only one bulb and a
> resistor.

That would be me.

> The only Resistor I have laying here is a
> 4.7 k-Ohm 1/2 watt type.

This is almost five times more resistance than what I suggested for
your MAXIMUM resistance value.

> I tryed wiring this in series with one bulp
> but I got nothing no light at all.
> Should there not be at least something.

Of course not. If there is not enough current flowing to heat the
filament adequately, so unless your vision extends into the infrared
you won't see squat. The value you used will permit 5ma to flow as
opposed to the 27ma starting point I suggested or the 40ma the bulb is
rated for.

> I also revisited the the 110 volt ac led again

So you have an led with a built-in dropping resistor calculated for
operation at 110 volts and you are trying to get it to run at 55?
Let's assume that your led was designed to operate at 1.4 volts and 20
ma. This would call for a dropping resistor of roughly 6k. Now let's
see what that would give us at 55 volts. We would have roughly 9ma
flowing through the led at .63 volts. This would be well below the
level at which you would expect to have a perceptible output from the
led. If you were to purchase an led without an integral dropping
resistor, it would be a simple matter to calculate the appropriate
value to make it work on 55 volts - keeping in mind that orientation of
the led in the circuit is important.

> Except when I stick it into a 110 volt ac outlet.
>

See above. Did you look at the link I gave you? I believe you would
learn some useful info there. I mean no offense, but I would also
suggest you spend a little time studying a good introductory
electronics text. There are several inexpensive ones that are quite
good and not huge - just concise introductions. I use then with high
school students, and if you like I can give you some titles and
authors.

Just curious - why don't you just put bleed resistors across the caps
and dispense with the lights? That has been the normal approach since
the vacuum tube days. If it is critical to make sure that the caps are
discharged it is a mistake to rely on a light which may simply have
burned out. That is why we have meters. (Or designs which turn the
light ON when it is safe - but that's a whole new project ;^)

Randy

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Dave Fisher" <dave@d...>
> wrote:
>> For your info LEDs' do work fine on DC, with the correct resistor -
> Although
>> for your
>> application probably not a good idea as the led's would take a LONG
> time
>> To drain the the caps.
>>
>> Ref the bulbs, you either have one of the bulbs shorted out or the
> 2 bulbs
>> are not
>> of equal voltage rating ?
>>
>> Good luck
>>
>> Dave Fisher
>>
>>
>> -----Original Message-----
>> From: Torsten [mailto:torsten@g...]
>> Sent: 14 December 2004 18:41
>> To: CAD_CAM_EDM_DRO@yahoogroups.com
>> Subject: [CAD_CAM_EDM_DRO] Re: Two Lamps?
>>
>>
>>
>>>> -----Original Message-----
>>>> From: Torsten [mailto:torsten@g...]
>>>> Sent: 25 October 2004 18:17
>>>> To: CAD_CAM_EDM_DRO@yahoogroups.com
>>>> Subject: [CAD_CAM_EDM_DRO] Two Lamps?
>>>>
>>>>
>>>>
>>>>
>>>> Got a question, I have a Powersupply delivering 55 volts DC in
> my
>>>> driverbox connected to a Caps to store and smuth out the
> current
>>>> having been zapped a few times I would like to hook up a little
>>>> light bulb to drain out the current after it is shut off.
>>>> Would also be nice for the visual feedback to see when the
> thing is
>>>> charged.
>>>>
>>>> On the first attempt I learned that a Led dose not work with DC
>>>> current.
>>>>
>>>> So now I am Looking at some Bulbs with a filament.
>>>> What I found is a "Miniature Bayonet base Lamp"
>>>> rated for 28 volt .040 amps I belive I should be able to wire
> two of
>>>> them in serial to make it work on my 55 volt system.
>>>>
>>>> Will this work?
>>>> Any thoughts, please share.
>>>>
>>>>
>>
>> Finally got the bulbs this week and tryed them out.
>> It worked sort of, the Light drained the power after about one
> minute or so
>> just what I wanted.
>> Strange thing is only one of the bulbs lighted up the other one did
> not seam
>> to be on.
>> Because they where wired in series I know electricity must have
> gone through
>> both of them.
>> What is going on, anybody know why only one light was on?
>> How do I fix it.
>>
>
>
>
>
>
>
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