jeffj@sfmin.UUCP (J.S.Jonas) (12/18/85)
[spritzensparken!]
I need the design for a power supply for a Sylvania C10/DC
Concentrated Arc Lamp, 10-watt, DC.
Here are the lamp specs:
AVERAGE CHARACTERISTICS
voltage across lamp 21 VDC
current through lamp 0.5 amps
candlepower 4.7 cp
diameter of light source .4mm.; 0.016 in.
This lamp has a negative volt ampere characteristic,
so must be provided with a suitable ballast whose resistance
will depend upon the d-c supply voltage. It is recommended
that a d-c voltage of at least 50 volts be used with
sufficient resistance in series with the lamp to
limit the current to 0.5 ampere. The lamp requires a momentary
starting potential of 1,000 volts or higher.
The bulb has two connections: cathode and anode.
Thanks in advance
Jeff 'more bright ideas?' Skot
{ihnp4 | allegra | mcnc} attunix ! jeffjlarry@kitty.UUCP (Larry Lippman) (12/22/85)
> I need the design for a power supply for a Sylvania C10/DC > Concentrated Arc Lamp, 10-watt, DC. > > Here are the lamp specs: > AVERAGE CHARACTERISTICS > voltage across lamp 21 VDC > current through lamp 0.5 amps > candlepower 4.7 cp > diameter of light source .4mm.; 0.016 in. > This lamp has a negative volt ampere characteristic, > so must be provided with a suitable ballast whose resistance > will depend upon the d-c supply voltage. It is recommended > that a d-c voltage of at least 50 volts be used with > sufficient resistance in series with the lamp to > limit the current to 0.5 ampere. The lamp requires a momentary > starting potential of 1,000 volts or higher. > > The bulb has two connections: cathode and anode. The design of a RELIABLE power source for a discharge lamp such as the above can be rather tricky. In general, you need the following circuit elements: 1. A constant current DC power supply providing the nominal 0.5 A current specified above 2. A current sensor with logic output to indicate when current is flowing from the constant current supply 3. A high voltage excitation source which can be AC or RF; this excitation source should be logic-controlled 4. A means of switching one lamp lead between the excitation source and the constant current supply When the power source is first turned on, the lack of DC current flow indicated by the logic output in (2) above starts a timer (1 to 5 sec) which simultaneously switches the lamp to the excitation source and turns on the excitation source; this action heats the lamp electrodes and ionizes the gas within the lamp. When the timer times out, the lamp is switched back across the constant current supply which then (hopefully) keeps the lamp alive. The above circuit is for an automatic starting lamp; you could simplify matters if you used a manual start button which operated a relay to turn on and switch in the excitation source. Due the high voltage necessary for starting, along with contact arcing, it would be inadvisable to use a momentary switch in place of a relay. Depending upon how exacting your application is, you could also replace the constant current supply with a simple rectifier/ballast resistor circuit. Be advised, however, that you may encounter significant lamp output variations should you NOT use a true constant current supply. I use a number of arc lamps in various instrumentation projects, but have always used commercial arc power supplies. Depending upon the seriousness of your application, I would strongly urge that you buy a commercial supply instead of trying to design and build one. Oriel Corp. of Stamford, Ct. makes many such supplies; a versatile small supply is their P/N 8500 or P/N 8510-1. If you would like to see representative schematic diagrams of arc source power supplies, try to find a manual for a Honeywell Visicorder (tm) recording oscillograph, or for a Bell & Howell/CEC recording oscillograph. Both of the above manufacturers use arc lamps in these instruments. === Larry Lippman @ Recognition Research Corp., Clarence, New York === === UUCP {decvax,dual,rocksanne,rocksvax,watmath}!sunybcs!kitty!larry === === VOICE 716/741-9185 {rice,shell}!baylor!/ === === FAX 716/741-9635 {G1, G2, G3} ihnp4!/ === === === === "Have you hugged your cat today?" ===