Ideas for a 125millisecond delay

[EOJ]

I have a question, say I have two light bulbs. I want one light bulb to light up instantaneously, then 125 milliseconds later I want the other light to light up. I have minimal experience with eletronics. I can read a schmatic and solder, but thats about it though. Thank you very much for your time and for helping me out. This is a project I'm heading up for school.

EOJ

 

[mramos1]

What type of bulbs?

Also, you want to light up 125ms after the first one is on I take it?

 

[RadioRon]

How precise do you want the 125mSec to be? Is it ok if it is approximately 125, like 100 to 150 mSec, or does it need to be exactly 125mSec?

 

[EOJ]

hey guys thanks for the quick reply, the light bulbs are commonly found in cheap flashlight I think the ratings are 2v and 1A to light up.

I would perfer the timing be as close to 125ms as possible, could you also explain to me what type of circuit can make that type of delay, and what you do have to do to vary the times.

Yes, the first bulb will light up once power is applied, then 125ms later the other bulb will light up.

Thank,

EOJ

 

[RadioRon]

"as close as possible" is saying more than you think. To get as close as possible will require a rubidium or caesium timing reference followed by a simple divider circuit using common logic family elements. An example of a Rubidium standard is the Standford FS725 which is only $2495.00. The digital divider might cost $3.50. This would get you within 0.000000625 mSec of exactly 125 mSec.

A more practical solution might be an OCXO crystal oscillator putting out 10MHz. This would be used to clock a triggered counter that is started at the beginning of your delay and that puts a pulse out at the end of the count which would be 1250000. This would get you within 0.00000125 mSec of 125 mSec. Such oscillators cost about $40. The divider logic would cost about $3.50.

Or if you don't mind an error of about 2 mSec, you could just use an NE555 timer IC. The data sheet includes a schematic for Monostable operation which will give you a triggerable time delay. You set the time delay using a combination of resistor and capacitor. To vary this usually means that you would use a variable resistor. This might cost you $2. Use a polystyrene or polyester capacitor for best time stability. See page 9 of the link:
https://www.electro-tech-online.com/custompdfs/2009/01/ne555.pdf

Now, this circuit gives you the timer, but you still need some circuitry to power each lamp. I guess the best arrangement is to provide power to the first lamp, the one that comes on immediately directly from a battery through a switch. The same battery voltage would be fed to the timer circuit and it would start to run its time delay when the switch is thrown.

The output of the timer would go from ground to battery voltage after the delay. This can't drive the second lamp directly, so you would need a transistor switch wired to the 555 output to drive the lamp.

 

[blueroomelectronics]

Light bulbs are not instant on anyway.

 

[EOJ]

Radio Ron,

You are a scholar and a gentelmen, you went above and beyond, thanks for the help. I was thinking about a 555 but I didn't think it would be that precise. I think I 'm going to go that route. I'll let you know how it works out.


Thanks again,


EOJ

 

[mramos1]

So what is this 2 cheap flashlight bulb/lamp with an accurate .125msec delay is for?

 

[Hero999]

Use LEDs, light bulbs can be very slow.