Auto testing bulbs

[Acetronics2]

Hi

just place an air winded coil around a reed "bulb" ... 10-15 turns * amp ( 20 - 30 turns for 1/2 amp ... 5 - 8 turns for 2 amps.)

in SERIES with your lamp.

reed contacts close when current flows.

Maaaaaagic, you told Maaaaaagic ???

circuits insulation as a bonus ... what else needed ???

Alain

[The Master]

Melanie, That does sound like a clever way of doing it but i think it might be a little over complicated. Using a single pin would be essential. If i can only have 11 bulbs per board then i need more than 7 boards and to address them correctly i need more than 4 DIP switches (taking up more inputs or using multiplexing). You said that i could use 1 pin but that would add even more components to the board. I understand roughly how your diagram works but im not too sure about the resistor. Last time i used a resistor in series with these bulbs i ended up with a fire. The zener probably takes care of that though (aswell as protecting the chip).

Acetronics, That sounds like a good idea. Its like the ammeter version but replacing the resistor/opamp/adc programming with a simple reed switch. Doing it this way instead of the way in my PCB layout means theres no relay so that transistor can be used to drive another bulb. I should probably do some testing first though to see if a single bulb can draw enough current to get a magnetig field strong enough. www.donsbulbs.com says that the smallest bulbs i have are 0.15A. Should that be "10-15 turns divided by amps"?

About the transistors. I used to use some ULN chips which i think were rated at 500mA but im not sure if thats per output or per all 8 outputs. Im sure there was a good reason i changed to transistors but i cant remember what it was. I always prefered the ULN chips. The transistors do seem to be more expensive but i suppose i dont have to have them in groups of 8. I know at first i had some ULNs soldered into PCBs and ended up blowing them up. Eventually i started putting DIL sockets in (should have done this from the start)

[Luciano]

Hi,

With one input pin you can test all your 22 bulbs.


(Click to enlarge the picture)

Best regards,

Luciano

[The Master]

I see where your going with that one. It looks similar to my relay idea but instead of switching the common wire for the bulbs over to the pin you are using diodes so it doesnt have to switch anything to run a test, all it has to do is turn 1 bulb on at a time. It looks a little confusing at first but its starting to make sense now. All the bulbs have to be turned on and you only turn off the one that you want to test. If i did use this method then i would have to be carefull how i programmed it. If all the boards turned all the lights on together i think it would be enough to blow the transformer.

To be honest i think i prefer Acetronics' idea. Its very simple and requires less components/board space. As long as a single bulb can draw enough current to turn the switch on then it should work

[Acetronics2]

Hi,

"the smallest bulbs i have are 0.15A. Should that be "10-15 turns divided by amps"?"

simple: 10 - 15 / 0.15 = ... 70 to 105 Turns.

... Take care for bending Reed bulbs wires ... always use a pair of pliers not to stress the glass !!!

Alain

[The Master]

I know. Ive broken pleanty of them as a kid. They make the wires really thick and strong too! Thanx for clearing up the formula confusion. I cant find any coils on Rapid that would do the job or even be modified to do the job. Im going to have to make my own so i suppose winding it around the reed switch itself would work. Is there any specific type of wire i should use? Ive got a few different kinds out of old transformers and motors etc

[The Master]

Luciano, Its more about the game really but i know a lot of pinball machines have patterns (mainly in attract mode) that turn on all the lights at the same time. I was going to buy a transformer from Rapid to handle all the bulbs. The one im looking at is 100VA 6V+6V. I was planning to use both of the secondaries to drive the 6V bulbs (split them evenly) and use both together for the 12V bulbs. As far as i understand 100VA means 100W so i should get about 8.3A at 12V. If i only think about the 6V bulbs then i should be able to get 16.6A by using both secondaries for 6V. That gives me about 110 bulbs which is about right for the small ones. There will be a few bigger ones on too and possibly some inverters for EL wire etc.

The idea was to program it so it cant turn on too many lights. I made that mistake before with an old transformer i had laying around. I dont think that was very powerfull though. I did also test an ATX PSU but it didnt work very well at all. Just a few lights at a time seemed to short it out but it was fine on the other transformer (till i tried to turn all the lights on). It could still have been a faulty PSU though. I have a few more laying around now so i might connect some bulbs into it when i get home and see how it goes

[Luciano]

If all the boards turned all the lights on together i think it would be enough to blow the transformer.

Hi,

Flashing all the lights together isn’t the purpose of a pinball machine?

With a 400-Watt ATX power supply you can have up to 15A @ 12V DC and 40A @ 5V DC.

How to Convert a Computer ATX Power Supply to a Lab Power Supply:
http://www.wikihow.com/Convert-a-Com...b-Power-Supply

Best regards,

Luciano