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[PIC] Can i use pic mcu as switch on dc-dc step up?

gatoulisss

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hello everyone,
i need your help.. i have a battery project witch is using an alarm siren to make loud sound when is needed, im using pic16f628a, a 3.7v cr123a battery to power it up and an sx1308 dc-dc step up converter for the siren. my problem is the consumption of these project, a) if i use pic pin output as step up input then the syren doesnt ring,b) if i use the battery positive pole as Vin and enable pin on the step up converter then the current draw is massive but it works as i would like it to, and finally c) if i use the enable pin of the step up converter and the battery as Vin then it works but not as good as using positive pole and again the current draw is big
without the step up in sleep mode my project draws 0,04mA and with step up using enable pin at sleep mode current draw is 0,4mA is big deference.
so i was wondering is there any way that i can use a pic pin as a switch to completely shut down the step up converter till the time i will need to use it?

thank you very much!
 

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barry

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Your description is pretty confusing.

1) Is the current draw "massive" all the time, or only when the siren is on?
1a) How much current does the siren draw? Obviously, a PIC output pin doesn't supply enough current to drive it.
2) Your comment "c)" makes little sense. What do you mean "works, but not as good"? Do things burst into flames?

I suspect your siren just requires a lot of current, and there's nothing you can do about that. That dc-dc convertor is very efficient, so if there's no load, it shouldn't draw much current at all.
 

gatoulisss

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Your description is pretty confusing.

1) Is the current draw "massive" all the time, or only when the siren is on?
1a) How much current does the siren draw? Obviously, a PIC output pin doesn't supply enough current to drive it.
2) Your comment "c)" makes little sense. What do you mean "works, but not as good"? Do things burst into flames?

I suspect your siren just requires a lot of current, and there's nothing you can do about that. That dc-dc convertor is very efficient, so if there's no load, it shouldn't draw much current at all.
sorry for the confusion
1)its massive all the time because the converter is all the time on, lets say about 35mA with output of 22v witch i dont need if the siren is off.
1a) yes i realize that thats why im wondering if these is any way to drive the converter usic pic as switch
2)lets say that in the second case (b) the output of syren is 110db and on the third case (c) is 95db this is what i mean not as good , but i again as i said the step up it draws lot of current even not enabled not as much as the b case but again big for the project
 

betwixt

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We need to know what the sirens power requirement is.
Your diagrams show a transformer driving a loudspeaker, is this what it really is? An alternative method of driving it may be sufficient, using a center tapped transformer and driving it 'push-pull' style or even a transformerless bridge configuration. The drive current can still be turned off completely using those methods.

Brian.
 

gatoulisss

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We need to know what the sirens power requirement is.
Your diagrams show a transformer driving a loudspeaker, is this what it really is? An alternative method of driving it may be sufficient, using a center tapped transformer and driving it 'push-pull' style or even a transformerless bridge configuration. The drive current can still be turned off completely using those methods.

Brian.
yes this is what i mean siren, its a transformer driving a buzzer that makes tones without the transformer the sound level is too low so i need for sure both transformer and step up to take the maximum output db
so i have to figure out how to drive the step up minimizing the current draw using something like switch and here is where i need help
 

barry

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AGAIN: WHAT IS THE CURRENT DRAW OF THE “SIREN”?

There‘s no reason that DC-DC converter should be drawing 35 ma If your transistor is truly off. according to the data sheet, Idle current is about 2ma.
 

gatoulisss

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AGAIN: WHAT IS THE CURRENT DRAW OF THE “SIREN”?

There‘s no reason that DC-DC converter should be drawing 35 ma If your transistor is truly off. according to the data sheet, Idle current is about 2ma.
i don't know what is the current draw of the siren because is not drawing current if the pic doesn't give signal to base of bc547
its not the siren the problem is how to use a 'type' of switch so the step up doesn't draw any current if its not in use
same circuit with step up disconnected draws 0,04mA current on idle , with step up connected with enable pin as switch it draws 0,4mA without changing anything else just connecting and disconnecting the step up module
 

barry

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i don't know what is the current draw of the siren because is not drawing current if the pic doesn't give signal to base of bc547
its not the siren the problem is how to use a 'type' of switch so the step up doesn't draw any current if its not in use
same circuit with step up disconnected draws 0,04mA current on idle , with step up connected with enable pin as switch it draws 0,4mA without changing anything else just connecting and disconnecting the step up module
Wow, so many problems in one response. You don't know what the current draw is "if the pic doesn't give signal"? Well, what if the pic DOES give signal????

Is this really a "siren" or is it a transformer driving a loudspeaker? Transformers don't work with DC, you know. Are you pulsing the transistor to generate the "siren"?

"It's not the siren...". Really? Because it sure SOUNDS like the siren is a problem, especially since you have no idea how much current it draws.

Maybe you have some wiring error because, as said before, the DCDC converter should only draw about 2mA with no load, not 35mA.
 

gatoulisss

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Wow, so many problems in one response. You don't know what the current draw is "if the pic doesn't give signal"? Well, what if the pic DOES give signal????

Is this really a "siren" or is it a transformer driving a loudspeaker? Transformers don't work with DC, you know. Are you pulsing the transistor to generate the "siren"?

"It's not the siren...". Really? Because it sure SOUNDS like the siren is a problem, especially since you have no idea how much current it draws.

Maybe you have some wiring error because, as said before, the DCDC converter should only draw about 2mA with no load, not 35mA.
ok sir,
first of all, this is the step up im using 2PCS DC-DC SX1308 2A Converter Step-UP Adjustable Power Module Booster - - Amazon.com
second as i said before the siren is a transformer driving a buzzer so if there is no tone there is no current draw and my problem is not the current draw when i have alarm but when is in idle mode... so the problem is NOT the siren (in idle it has no consumption or no consumption to count)
so in this step up i desolder the en pin (witch was soldered to Vin) so i can drive it through pic pin but again if the step up is connected the current draw is big even with enable off

i want a way to drive the step up by completely shuting it down and when alarm happens to power it up so with this way i could minimize the current draw in idle mode... is there any way to do this? THIS IS what im asking for
 

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What we are trying to tell you is the solution to your problem is probably not to boost the voltage at all. Doing it that way is inefficient, costs more and drains the battery faster.

If the siren, for which you give us no information, can be driven in a different way you may not need the step-up converter at all and the overall current consumption will also be lower.

Brian.
 

barry

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So its not a siren, but a buzzer? That gives us exactly no information.
 

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