Switch wiring question

[RIVFADER]

Hi all,
I would post this in the Modders forum but don't have access to it yet, so I will post it here in hopes that someone knowledgable replies.

I am planning my first attempt at modding an e cig and have been somewhat confused on how I am going to wire my switches. My plan is to use a main kill switch immediately after the positive battery connection (a switch that is overrated for my use, like something rated for 3Amps). However I would like to use a smaller tactile switch but have noticed they are only rated for generally 50mA.

My idea is to wire a resistor coming from the atomizer output in line with a tactile switch, in theory knocking down the amperage to under 50mA, and that switch connecting to the negative side of the battery to complete the flow of electricity. I would use this switch as a "fire" switch to activate the atomizer.

Currently this is the only way I can see dropping the amperage to a level that a small tactile switch can safely handle. Does anyone have any other recommendations, or have tried this configuration? I'm not currently at my home location, but eventually was going to put this all down on a breadboard and meter the voltage and amperage flowing through the circuit.

Thanks for the help.

 

[dormouse]

You can read the modding forum - try going there and using Search Forum to search for tactile

And you don't need 5 posts - you need 5 non-spammed non-sequential posts or replies and then a 1 hour wait. Greet or help a few people.

A couple of threads about tactiles

http://www.e-cigarette-forum.com/fo...ple-touch-switch-pass-thru-under-15-00-a.html

http://www.e-cigarette-forum.com/forum/battery-mods/175694-mosfet-question-tactile-switch.html

 

[Allan.GH]

Don't use inline resistors.

The atty will not fire at 50mA.

Get a switch rated for a higher current (3 Amps is the absolute minimum I'd use), unless you're planning to use a PWM module at a fixed output, or an LDO regulator or MOSFET to handle the atty current.

Additionally, don't try breadboarding circuits that are carrying more current than the breadboard contacts are rated for. You will cook the contacts (I can't tell you how many times I've done that, and breadboarding/prototyping modules aren't all THAT inexpensive). I don't know what specific breadboarding product you're working with, and it's limitations, so I can only give you a general rule of thumb, here. I keep my breadboarding to under an Amp, because the contacts heat up fast, and lose their tempering.

 

[tj99959]

See the tiny white dot at the bottom?

That is the smallest 50ma switch I could find.
The + wire runs from the bat to the switch, and from the switch to the center post of the connector.
The - wire runs from the bat to the housing of the connector.
That's it!!!
Since that mod only cost $2.20 to make, it is the one I use when I'm doing things where my PV might get damaged or broken (like duck hunting)
Been using it since July, switch is still working fine.

 

[Allan.GH]

If the switch used is reminiscent of this C-K unit:

...then, it's likely the rated current of your switch is higher by several orders of magnitude (actuator diameter is 3mm in the photo).

While I don't know the specifics of the switch you used, it certainly looks like the several varieties of the above switch that I have in my inventory (ranging from 3A to 6A @ 120VAC). You can see in the photo that, the switch is rated for 1A breaking current @ 250VAC; but also rated 3A @ 120VAC. In general, as you lower the open circuit voltage, you gain some overhead in switching current; however, you'll finally reach a point of diminishing gains.

Contact resistance, arcing and closed-circuit heating are the primary concerns in switching loads; and, the majority of complaints I've read about mods have to do with what really amounts to an inadequate switch.

The "de rigueur" of engineering dictates that adequate margins be incorporated into anything you design, and the maxim I followed in college was "spec your limits, add 10%, then double it". That's just my instinct, and that's what fueled my earlier mention of switches.

Can a 50 mA switch work driving an atty?

That depends on the specifics of the switch ratings, the particular circuit it's used in, and how often it's being used.

Will it handle constant daily use for a couple of years, driving 1.5Ω DCC or a 2Ω atty, at 6 to 8 Volts?

Despite the fact that the atomizer coil resistance increases when it's heating, I'd still bet my money against it.

Anyway, I'm not haranguing about it or trying to tell anyone what to do. I'm just trying to explain why I said what I did, earlier.

 

[cyberwolf]

The right way to do it is to use a switch with a higher rating or a mosfet type arrangement that only uses the switch to activate the relay. That said, I have used 50mA switches on a couple of 3.7v mods with no ill effects or unacceptably short life. Keep in mind that these were cheap box mods that were not going to upset me if they failed.

 

[tj99959]

If the switch used is reminiscent of this C-K unit:

...then, it's likely the rated current of your switch is higher by several orders of magnitude (actuator diameter is 3mm in the photo).

While I don't know the specifics of the switch you used, it certainly looks like the several varieties of the above switch that I have in my inventory (ranging from 3A to 6A @ 120VAC). You can see in the photo that, the switch is rated for 1A breaking current @ 250VAC; but also rated 3A @ 120VAC. In general, as you lower the open circuit voltage, you gain some overhead in switching current; however, you'll finally reach a point of diminishing gains.

Contact resistance, arcing and closed-circuit heating are the primary concerns in switching loads; and, the majority of complaints I've read about mods have to do with what really amounts to an inadequate switch.

The "de rigueur" of engineering dictates that adequate margins be incorporated into anything you design, and the maxim I followed in college was "spec your limits, add 10%, then double it". That's just my instinct, and that's what fueled my earlier mention of switches.

Can a 50 mA switch work driving an atty?

That depends on the specifics of the switch ratings, the particular circuit it's used in, and how often it's being used.

Will it handle constant daily use for a couple of years, driving 1.5Ω DCC or a 2Ω atty, at 6 to 8 Volts?

Despite the fact that the atomizer coil resistance increases when it's heating, I'd still bet my money against it.

Anyway, I'm not haranguing about it or trying to tell anyone what to do. I'm just trying to explain why I said what I did, earlier.

Nope it's this switch

Description
These press in nicely to a 3/32" hole and stay without the need for adhesives.. Rated at 12vdc, 50ma but they provide plenty of current to keep an atty going.. I love these switches but the touch is so light that you should definitely have a master on/off switch on your project for when you stash it in your pocket or purse. When I use these, I automatically flip on the master switch, vape, flip off the master and put it back in my pocket.. I have some of these going on 5 months old now without a broken one yet. Works great on mods because of the small size. Price is per switch. Other items shown are for size comparison only and not included. Sample Projects

I used it because there is only so much room in a 2xAAA box when you put the carto inside the box.
That entire mod is roughly the same size as one 18650 battery. (23x63mm)

 

[Cool_Breeze]

While I don't know the specifics of the switch you used, it certainly looks like the several varieties of the above switch that I have in my inventory (ranging from 3A to 6A @ 120VAC). You can see in the photo that, the switch is rated for 1A breaking current @ 250VAC; but also rated 3A @ 120VAC. In general, as you lower the open circuit voltage, you gain some overhead in switching current; however, you'll finally reach a point of diminishing gains.

How does (or doesn't) AC current rating of switches relate to DC current? ...thanks.

 

[RIVFADER]

I have seen some voltage regulators with control pins but I haven't been able to find how the control pin relates to the regulator... It seems to me the control pin is like a gate that will allow voltage to pass from the Vin to the Vout on a regulator... is this what it is doing? And how would I wire it? Is the regulator an open circuit until the control pin is connected to the Vin? or Vout? or the Ground of the regulator? I am also curious about the AC rating of switches and how (if at all) they relate to how much DC voltage they can handle.

 

[Allan.GH]

Sorry....I've been away all day, and only now got back:

I understand the space limitations that you were working with and, sometimes that dictates parts choices for us. Just be aware that the switch is definitely the weakest link in the chain.

Switching involves a lot of issues that I won't go into, here, but I will hit the "high points".

The DC ratings of switches and mechanical relay contacts are typically much lower than AC ratings. It is not uncommon to see AC current ratings for switches specified at 240 to 250 Volts, with the identical current rating specified at a maximum DC voltage of 30 Volts. There are a lot of trade-offs involved, and they depend on things like contact patch area, contact resistance, make and break bounce, break angle...yadda-yadda-yadda.

This is because the zero-crossing of the constantly varying AC waveform will permit switch transitions at times of non-peak current demand.
It's something of a statistical issue. Sometimes it's at peak value. Other times it's at zero. Still more times it's somewhere in-between.

Current demand for a DC load, at switch closure, is typically at peak demand all the time, because the DC waveform is non-varying, and the load will require maximum current.

With respect to opening a switch supplying resistive heating or incandescent lighting loads, current demand is generally not at peak.

In the case of a resistive heating (or incandescent lighting) loads, the load filament or heating coil temperature is at maximum; which increases the load resistance and, in turn, reduces the current consumption of the load. This causes a situation wherein closing a switch is always most destructive to the switch contacts, and opening the switch is somewhat less so; because there is never a zero crossing condition experienced with the DC supply.

Making the situation worse, current always flows in the same direction in a DC circuit.

Within the switch, one contact is always positive and the other contact is always negative. Since full switch contact is never instantaneous, arcing takes place between the switch contacts. The result of this arc is a melting of the contact metal, which then deposits to the negative contact, because it is cooler. The same thing happens when a switch opens. It's not instantaneous. Arcing occurs. Metal is transferred from the positive contact to the negative contact.

In an AC circuit, metal migration is usually back and forth between contacts, because the polarity of the AC waveform is constantly switching back and forth.

However, because the polarity of the contacts in DC load switching are always the same, one contact gets somewhat slagged, and the other is continually pitted. At some point during the switch life, the contact area will become small enough to initiate heating of the switch contacts. In this case, the switch conductors may deform because of annealing, resulting in a switch that won't close; or the contacts may weld themselves together, resulting in a switch that won't open. Kind-of a coin-toss.

Switch contacts can be protected from this effect by using a technique called "snubbing", which I won't go into here--there are probably some very good references to be had on the Internet--but it essentially consists of placing a series connected resistor and capacitor across the external switch terminals. Snubbing vastly increases the service life of the switch, but I've never seen it implemented in any mod to date.

So, really, DC ratings are markedly less than AC ratings for the same set of switching contacts.

____________________________

V Regs....well, I've really gone on too long but, in just pulling a couple part numbers off the front of my brain, it might be best if give you a couple of documents to look-over and decide what's best for your situation:

General-case linear fixed regulators

General-case linear adjustable regulators

Anyway, I hope that's of help.