Hi guys,
New to this site. Might have the wrong topic area. I have a project I want to put together. I don't know a lot about electrical circuits so no doubt I'll be back for more info later. But in the mean time I need to find out the parts I need to acquire. So to the point, I'm looking for a timer to countdown from probably 60-90 minutes.I want to make it as small as possible and someone suggested a 555 chip. Doing a little reading this chip would not meet my requirements? After the timer expires my intention is to have the circuit open and release a compressed spring with a needle, to puncture a 12 or 16g co2 canister. Any suggestions or ideas greatly appreciated. Or if anyone knows of someone doing this before I'd love to know how it was set up and how small the unit can be while still being operational. Thinking to use a 9v battery if possible to keep the size down, but unsure if thats viable either.
Cheers again in advance.

 

Welcome to AAC!
A 555 won't do it reliably. A CD4060-based circuit, or a suitably programmed MCU, would be better. That would drive a MOSFET to supply current to an actuator for releasing the spring.

 

I don't know a lot about electrical circuits so no doubt I'll be back for more info later. But in the mean time I need to find out the parts I need to acquire.

Walk into your local hardware store and they will have timers for you.

With your combination of goal / timing requirement, your lack of skills and what it takes to do what you want to do, you are far better off buying off the shelf timers.

 

You're better buying a ready-made timer like these modules,or similar,, 0-999 minutes, 12v..


http://m.ebay.co.uk/itm/Trigger-Cyc...%3A3b0527de1580a6228366dcb8fff7b451%7Ciid%3A5

 

Hi guys,
New to this site. Might have the wrong topic area. I have a project I want to put together. I don't know a lot about electrical circuits so no doubt I'll be back for more info later. But in the mean time I need to find out the parts I need to acquire. So to the point, I'm looking for a timer to countdown from probably 60-90 minutes.I want to make it as small as possible and someone suggested a 555 chip. Doing a little reading this chip would not meet my requirements? After the timer expires my intention is to have the circuit open and release a compressed spring with a needle, to puncture a 12 or 16g co2 canister. Any suggestions or ideas greatly appreciated. Or if anyone knows of someone doing this before I'd love to know how it was set up and how small the unit can be while still being operational. Thinking to use a 9v battery if possible to keep the size down, but unsure if thats viable either.
Cheers again in advance.

What are you hoping will happen when a 12 oz can of co2 is punctured?

 

He's hoping it will put out the fire started by his lithium battery being over-charged .

 

Do you have the mechanism for holding the compressed spring ? Maybe an electro magnet, & if so how much current does it need to hold ? A 555 will work but low leakage cap. is fairly large, 35 mm X 60 mm.

 

This smells battery powered. What is the power source for the timer and for the spring release mechanism? There are tons of digital timers modules on ebay for cheap if they match your power and output requirements. If not, CD4060 timer circuits are relatively simple.

Do you need only one time period, or does it have to be adjustable?

How accurate and repeatable does it have to be? For example, 75 minutes plus/minus 0.01 seconds, or anywhere from 70 to 80 minutes plus/minus 1 minute?

ak

 

Hi guys,
New to this site. Might have the wrong topic area. I have a project I want to put together. I don't know a lot about electrical circuits so no doubt I'll be back for more info later. But in the mean time I need to find out the parts I need to acquire. So to the point, I'm looking for a timer to countdown from probably 60-90 minutes.I want to make it as small as possible and someone suggested a 555 chip. Doing a little reading this chip would not meet my requirements? After the timer expires my intention is to have the circuit open and release a compressed spring with a needle, to puncture a 12 or 16g co2 canister. Any suggestions or ideas greatly appreciated. Or if anyone knows of someone doing this before I'd love to know how it was set up and how small the unit can be while still being operational. Thinking to use a 9v battery if possible to keep the size down, but unsure if thats viable either.
Cheers again in advance.

Let's let the "puncture a CO2 canister after a set period of time" aspect of your project stay on the back shelf (so that we don't have to consider whether you are violating the forum rules).

You want a timer that is as small as possible that counts for something in the 60 to 90 minute range.

How small is small enough? We aren't mind readers, so for some people "as small as possible" might be satisfied by "it fits in a box about the size of an apple" while for others "it fits in a box the size of a book of matches" might not even be close to being small enough.

The same thing on the time range. Do you need it to be adjustable over that range, or will it just be a fixed time length that will happen to fall within that range? In either event, how accurate and precise does it need to be? If you settle on 75 minutes, would it be okay if it actually expired after 72 minutes or 80 minutes? Or if you use it 20 times how close do all of the times need to be to each other, irrespective of how close they are to the nominal time span?

What is this going to be powered by?

How many of these do you need to make? If it's just one or two, then the "best" solution might be very different than if you are going to be making dozens of them -- and that solution might look very different than if you are making thousands of them.

Are you planning to get involved with electronics and projects on a regular basis, or is this a one-time thing? If the former, then it might make sense to pursue an MCU-based solution and accept the overhead, both in learning and in hardware, that is involved. If not, then it probably makes more sense to either go with an off-the-shelf solution (provided it meets your space, power, and other requirements) or use a combination of a 555 timer and a counter/divider IC.

The more you can flesh out these variables, the better the quality of the advice you will likely receive. Don't worry, we understand that you don't know all the questions that need to be asked. That's fine. Tell us what you think the important things are and then we will be more than willing to try to ask the right questions of you.