# [EVDL] Vacuum tube for precharge



## EVDL List (Jul 27, 2007)

We discussed the idea of using a vacuum tube for a precharge resistor 
recently. I was shopping at my local surplus store (AxMan in 
Minneapolis), and picked up a couple tubes that should work for this; a 
12AX4 and a 12D4. They have a 12 volt filament, and are intended as a 
damper diode in a TV set. The diode is rated at 5000 volts PIV, 1 amp 
peak, and has a forward voltage drop of 32 volts at 125ma (equivalent to 
a 256 ohm precharge resistor). They both fit in an 8-pin octal socket, 
which makes them easy to mount (a modern relay socket).

Anybody want one to experiment with? $5 plus shipping. I'll include a 
copy of the data sheet from my tube manuals.

-- 
Lee A. Hart | Ring the bells that still can ring 
814 8th Ave N | Forget the perfect offering
Sartell MN 56377	| There is a crack in everything 
[email protected] | That's how the light gets in -- Leonard Cohen 

_______________________________________________
General EVDL support: http://evdl.org/help/
Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

How would this be an improvement over my 60 watt lightbulb?



> Lee Hart <[email protected]> wrote:
> > We discussed the idea of using a vacuum tube for a precharge resistor
> > recently. I was shopping at my local surplus store (AxMan in
> > Minneapolis), and picked up a couple tubes that should work for this; a
> ...


----------



## EVDL List (Jul 27, 2007)

> Lee Hart <[email protected]> wrote:
> > > We discussed the idea of using a vacuum tube for a precharge
> > > resistor recently...
> 
> ...


----------



## EVDL List (Jul 27, 2007)

> On 19 Sep 2009 at 11:56, storm connors wrote:
> 
> > How would this be an improvement over my 60 watt lightbulb?
> 
> ...


----------



## EVDL List (Jul 27, 2007)

Lee,

I've actually built one of these for testing -- I posted about it on a 
"steampunk" forum, because to looks very retro:

http://brassgoggles.co.uk/forum/index.php/topic,13593.0.html

It works, but one of the "problems," is that the tubes take a while to 
warm up enough to allow current to pass. Usually it's nearly 10 seconds 
before any current flows.

I used two 12AL5 dual diode modules. The particular setup shown at that 
website is a precharge AND discharge module -- it uses one tube for 
each. The toggle switch is a 3 position SPDT for charge / neutral / 
discharge.

Now I just have to find time to get to the garage. *sigh*




> Lee Hart wrote:
> > We discussed the idea of using a vacuum tube for a precharge resistor
> > recently. I was shopping at my local surplus store (AxMan in
> > Minneapolis), and picked up a couple tubes that should work for this; a
> ...


----------



## EVDL List (Jul 27, 2007)

> Eric Poulsen wrote:
> > I've actually built one of these for testing -- I posted about it on a
> > "steampunk" forum, because to looks very retro:
> > http://brassgoggles.co.uk/forum/index.php/topic,13593.0.html
> ...


----------



## EVDL List (Jul 27, 2007)

Could you use a power triode instead of a diode and bias the grid so no current flows. Then you could power the tube when you open the car door or some other activity. Then by the time you trigger the pre-charge by removing the bias the filament would be warm and the current would flow right away. I saw some power triodes up in the 6KW range but they were heavy and required forced air cooling.

Lawrence

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Lee Hart
Sent: Tuesday, September 22, 2009 3:58 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Vacuum tube for precharge



> Eric Poulsen wrote:
> > I've actually built one of these for testing -- I posted about it on a
> > "steampunk" forum, because to looks very retro:
> > http://brassgoggles.co.uk/forum/index.php/topic,13593.0.html
> ...


----------



## EVDL List (Jul 27, 2007)

> Eric Poulsen wrote:
> 
> > I've actually built one of these for testing -- I posted
> > about it on a "steampunk" forum, because to looks very retro:
> ...


----------



## EVDL List (Jul 27, 2007)

You could skip ahead 50 years and use a PNP BJT

e.g.

2SA1381:
beta ~= 40
300vCE
$.40

1 Meg pullup to emitter. Relay or NPN current sink switches on 1mA
base pull-down. Gives you ~40mA precharge.

--
Martin K.

_______________________________________________
General EVDL support: http://evdl.org/help/
Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

> Harris, Lawrence wrote:
> > Could you use a power triode instead of a diode and bias the grid so
> > no current flows. Then you could power the tube when you open the
> > car door or some other activity. Then by the time you trigger the
> ...


----------



## EVDL List (Jul 27, 2007)

> Roger Stockton wrote:
> > 11 seconds is a typical spec for filament warmup time, but you may
> > still be able to speed the precharge up by switching to a beefier
> > diode.
> ...


----------



## EVDL List (Jul 27, 2007)

> Martin K wrote:
> > You could skip ahead 50 years and use a PNP BJT
> > 2SA1381:
> > beta ~= 40
> ...


----------



## EVDL List (Jul 27, 2007)

> ----- Original Message -----
> From: "Lee Hart" <[email protected]>
> To: "Electric Vehicle Discussion List" <[email protected]>
> Subject: Re: [EVDL] Vacuum tube for precharge
> Date: Tue, 22 Sep 2009 22:12:01 -0500
> 
> 


> > Martin K wrote:
> > > You could skip ahead 50 years and use a PNP BJT
> > > 2SA1381:
> > > beta ~= 40
> ...


----------



## EVDL List (Jul 27, 2007)

> Lee Hart <[email protected]> wrote:
> 
> > Except I think the transistor would be destroyed the first time you use
> > it. Look at the power dissipation in that transistor. Suppose you have a
> ...


----------



## EVDL List (Jul 27, 2007)

> Lee Hart <[email protected]> wrote:
> >> Except I think the transistor would be destroyed the first time you use
> >> it. Look at the power dissipation in that transistor. Suppose you have a
> >> 144v pack; 144v x 40ma = 5.76 watts!
> ...


----------



## EVDL List (Jul 27, 2007)

> Roger Stockton wrote:
> > Eric Poulsen wrote:
> >
> >
> ...


----------



## EVDL List (Jul 27, 2007)

> Eric Poulsen wrote:
> 
> > Roger Stockton wrote:
> > >
> ...


----------



## EVDL List (Jul 27, 2007)

> Roger Stockton wrote:
> > Eric Poulsen wrote:
> >
> >
> ...


----------



## EVDL List (Jul 27, 2007)

>> Yeah, but it's cheap, available, and physically small.



> Roger Stockton wrote:
> > ...and slow ;^> But, if you are happy with the precharge speed you
> > get with it, there is certainly no reason to change.
> >
> ...


----------



## EVDL List (Jul 27, 2007)

> Eric Poulsen wrote:
> > If you want a fast precharge ( less than 5 seconds), then maybe using a
> > tube isn't the way to go at all?
> 
> ...


----------



## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> 
> > Most of the precharge time is the time for the tube to warm
> > up. The spec is the same (11 seconds) for both the 12AL5 and
> ...


----------



## EVDL List (Jul 27, 2007)
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----------



## EVDL List (Jul 27, 2007)

> Roger Stockton wrote:
> >> I think Eric hit the nail on the head: one probably shouldn't use a
> >> tube precharge circuit if they want a "fast" precharge, but if
> >> sub-13 seconds is fast enough, the proper choice of tube can
> ...


----------



## EVDL List (Jul 27, 2007)

I have a bunch of nixie tubes (and driver parts) just a few feet from 
the EV project -- I was just going to make a clock.

Martin K wrote:
>


> Roger Stockton <[email protected]> wrote:
> >
> >
> >> I think Eric hit the nail on the head: one probably shouldn't use a tube precharge circuit if they want a "fast" precharge, but if sub-13 seconds is fast enough, the proper choice of tube can certainly suffice.
> ...


----------



## EVDL List (Jul 27, 2007)

Roger,

I didn't see much of a _voltage change_ (from zero) with the 12AL5 until 
10 or so seconds. Also, I use both plates -- total current is closer to 
108 mA.

And stop calling my tubes wimpy! ;-)

-- Eric



> Roger Stockton wrote:
> > I'm not sure if you are just playing devil's advocate here ;^>
> >
> > Yes, all of these tubes have heaters spec'd for an 11s warmup, and yes, the precharge time will still be dominated by the heater warmup delay. However, after 11s warmup, the 12AL5 is capable of just 54mA while the beefier tubes can deliver 1A+; since the current increases smoothly from 0 after some amount of warmup to rated current after 11s, the beefier tube is going to provide more 'area under the curve' and will have precharged the caps more by the time it is fully warm than the wimpy 12AL5 will have.
> ...


----------



## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> > Another solution is to use a tube with a "harp" filament. This type was
> > found in some expensive tubes for mobile radios. They have an
> > indirectly heated cathode, but warm up almost instantly (like a light bulb).
> ...


----------



## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> > Roger Stockton wrote:
> >
> >>> I think Eric hit the nail on the head: one probably shouldn't use a
> ...


----------



## EVDL List (Jul 27, 2007)

> Eric Poulsen wrote:
> Lee Hart wrote:
> >> Another solution is to use a tube with a "harp" filament.
> 
> ...


----------



## EVDL List (Jul 27, 2007)
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=


----------



## EVDL List (Jul 27, 2007)

> Martin K wrote:
> >>>> Bonus points for a nixie tube ammeter in the car.
> >>>>
> >>> It's hard to see what advantage nixie tubes would have over other
> ...


----------



## EVDL List (Jul 27, 2007)
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----------



## EVDL List (Jul 27, 2007)

> Eric Poulsen wrote:
> 
> > I didn't see much of a _voltage change_ (from zero) with the
> > 12AL5 until 10 or so seconds. Also, I use both plates --
> ...


----------



## EVDL List (Jul 27, 2007)

> > Lee Hart wrote:
> >> Roger Stockton wrote:
> >>
> >>>> I think Eric hit the nail on the head: one probably shouldn't use a
> ...


----------



## EVDL List (Jul 27, 2007)

Robert Johnston wrote:
>


> Eric Poulsen <[email protected]> wrote:
> >
> > Erm... F1 doesn't use analog gauges.
> >
> ...


----------



## EVDL List (Jul 27, 2007)

My original test:

35V dc power supply
6000uF cap bank
0 to 30V took 18 seconds, with no change until about the 10 second mark.

I don't think the tubes act as a constant resistance when used to charge 
to ~ 150V -- Lee, do you know?

> Sorry, no offense intended ;^>
>
> Perhap I'll have to see if I have both the 12AL5 and one of the beefier alternatives onhand and measure them both into the same cap bank.
>
> If I do, I'll post the results.
>
> 

_______________________________________________
General EVDL support: http://evdl.org/help/
Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

> Eric Poulsen wrote:
> > My original test:
> >
> > 35V dc power supply
> ...


----------

