Current Activated Buzzer Circuit Advise 1

[rocksolidsr]

I'm trying to have a buzzer beep when current is applied to a transformer, spec sheet attached. I have an idea of what I would do I just want to run it by you guys and see what you think

I was thinking of using one of these current sensors

http://search.digikey.com/scripts/d...wt.mc_id=Dxn_US_T091_Catlink;name=398-1000-ND

and run the output wire through it and use the output of that to run this circuit to make the buzzer beep.

http://www.doctronics.co.uk/555.htm#pb_04

for my buzzer circuit i used an NPN transistor and a 5v buzzer and that works fine when a voltage of 2.5V or greater is applied, I'm just not sure how to trigger it.

Do you think this would work, the output of the transducer is high voltage, high frequency >20khz


Ok I measured the output of the transducer using this current probe

http://www.aemc.com/products/pdf/1201.51.pdf

here is what i got with the probe set to 100mA/V
Cyc RMS = 472mV
Rise Time = 14.84us
Fall Time = 18.20us
Pos Width = 24.7us
Neg Width = 24.20us
Freq = 20.45kHz
Period = 48.90us
Mean = 68.7mV
Pk-Pk = 1.54V

so from those measurements I am seeing that I would probably need to measure current up to 154mA?

i'm kinda stumped here, i'm trying not to mess with the original circuit if at all possible, what is the easiest way to detect output from the transformer and have that output a voltage signal of at least 2.5V

I have the buzzer circuit working with a 555 timer and a npn transistor but i'm not sure how to only activate it when there is output from the transformer

any help would be greatly appreciated thanks.
attached is the transformers spec sheet

 

[itsmoked]

The output from your current transformer, what is the highest voltage you can get out of it when your power transformer is on? The higher the resistance value of the burden resistor the higher the voltage. But we need to know what that voltage is. (If I even understand your scheme..)

If the voltage is higher than about 2.5V you can use a FET as a switch to power up your entire 555 buzzer circuit.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[rocksolidsr]

the output of the transformer is approx 230VAC
i have attached the picture of what i have to work with, some how i need to detect when there is output from the transformer

 

[rocksolidsr]

 

[itsmoked]

Sorry I was thinking your "current sensor" was a transformer. On second look it's not. It also puts out a varying signal that swings 0.5 to 4.5V.

Use a voltage comparator to trip at a variable voltage, you can set with a resistor value, or with a pot, to run a FET to turn on your 555 circuit.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[rocksolidsr]

is there any way to accomplish this without the need for an external 5V, like is there any way to use the output of the transformer to power my 555 timer

 

[OperaHouse]

Is this a GO-NO GO application? You could just run a wire through a small toroid current transformer and rectify it to a relay or run the buzzer electronics.

 

[rocksolidsr]

yes it is just a go no go situation, do you have any recommendations on toroid and rectifiers for my application

thanks

 

[rocksolidsr]

would something like this work

http://www.inductech.com/current_sensing_transformers/current_sensing_csi0T.htm

 

[flexoprinting]

"the output of the transformer is approx 230VAC
i have attached the picture of what i have to work with, some how i need to detect when there is output from the transformer"

Why not simply hook up a buzzer with rated voltage on secondary of xformer? The transformer is not high frequency is it?

http://www.wolfautomation.com/Product.aspx?ProductID=791

 

[rocksolidsr]

yes the transformer is high frequency approx 21khz

 

[OperaHouse]

Some things to consider is how the added inductance and extra load on the 21khz inverter will affect normal operation. You are lucky to have a lot of options for transformers at this frequency. When I developed a similar product line I found using a voltage doubler was cost effective. Less turns was lower cost and the assemblers didn't have to deal with as fine a wire. Remember to use a diode with fast enough recovery.

 

[rocksolidsr]

i don't have the option of changing the transformer i just need to turn on a buzzer when there is live output from the transformer

 

[OperaHouse]

My trail of thought and that of rocksolidsr was to dump the hall effect sensor and have a simple GO-NO GO setup using simple current sense transformer. That sense transformer would provide all the power to operate the tone generator. If making a number of these, that might be a better way to go. If using the Hall effect sensor, a simple threshold detector using a LM339 would work.

 

[flexoprinting]

Hello operahouse
The trail of thought you have is for sure a more interesting way to proceed, LPS for that.

Thanks

 

[rocksolidsr]

so i got one of these

http://www.inductech.com/current_sensing_transformers/current_sensing_csi0T.htm

and put one of the output wire of the transformer through it and i'm getting about 1.5VAC output from it. Does anyone have any ideas how i can use that signal to power a buzzer?

 

[OperaHouse]

Which one did you actually get, the 50 turn? It would seem you need a second pass of wire through the center hole and a voltage doubler. That would look like two half wave rectifiers connected in series. Two capacitors in series with one leg of the transformer connected to the center. Small glass switching diodes should be ok. This should give you about 5V.

 

[rocksolidsr]

i got the CSI-0100, what do you mean by second pass of wire through the center hole?

 

[OperaHouse]

It means that you probably should have bought the 200 turn version. You have a 0.170 hole and if you can pass the wire through a second time to effectively double the current. 1.5V is a little low to rectify.

 

[zappedagain]

This might work on 1.5V:

http://www.edn.com/article/CA6632374.html?spacedesc=designideas&industryid=44217

John D