Suitable transistor

Thread Starter

Wolf5824

Joined Aug 2, 2022
6
Hi everyone
I want to connect a 40khz transducer to a Power supply & control it with a transistor

But i want to connect the ground to the transducer through the transistor

& the transistor should be a high speed switching transistor that works with maximum of 5v or lower going to the base

What is the best transistor ?
 

dl324

Joined Mar 30, 2015
14,905
Welcome to AAC!
  1. Are you going to use the transistor as a switch?
  2. What is the transducer impedance and voltage?
  3. What is driving the transistor?
  4. What are the voltage levels?
  5. How fast do you plan to switch the transducer?
  6. Does it have to be a BJT?
 

crutschow

Joined Mar 14, 2008
30,454
Not enough info--
What is the transducer voltage?
What is the transducer current?
How fast do you want to turn it on and off?
 

Thread Starter

Wolf5824

Joined Aug 2, 2022
6
Welcome to AAC!
  1. Are you going to use the transistor as a switch?
  2. What is the transducer impedance and voltage?
  3. What is driving the transistor?
  4. What are the voltage levels?
  5. How fast do you plan to switch the transducer?
  6. Does it have to be a BJT?
To answer your questions
1-yes

2-12vdc ( SKU: BFL740-3 Ultrasonic Level Sensor) link( https://www.bellenviro.co.uk/ultrasonic-level-sensor-0-3-metre-range-4-20ma-24v-dc.html )

3-an arduino generating 40khz signal @ maximum voltage 5v

4-a 12vdc @ 1Amps maximum Will be switched on & off by the transistor
(the transistor will be connected to the ground & it will be connecting & disconnecting the ground lead to the transducer)

5-switching speed 40000 times a second (40khz)

6-any suitable transistor (maximum base voltage 5v +high speed switching 40khz)
 

Ian0

Joined Aug 7, 2020
5,885
That’s an ultrasonic level sensor, not an ultrasonic transducer. It needs a 12V DC supply. I suspect that if you switch it on and off 40000 times a second it’s not going to be too happy.
 

MrChips

Joined Oct 2, 2009
26,792
Agreed. Read the datasheet very carefully.

The unit can be ordered with different types of outputs:
Alternative Outputs on request: 0-5V, 0-10V, 0-20mA, 4-20mA(3-wire), RS485.
 

Thread Starter

Wolf5824

Joined Aug 2, 2022
6
Need spec of transducer, power supply voltage and details of the required switching performance
Transducer specs 12vdc ( SKU: BFL740-3 Ultrasonic Level Sensor) link( https://www.bellenviro.co.uk/ultrasonic-level-sensor-0-3-metre-range-4-20ma-24v-dc.html )

12vdc power supply

40000 times a second switching speed

I'm connecting the transistor to the ground lead to protect it

May logic is ( by using the transistor to connect & disconnect the ground lead to the transducer
No current or voltage will be passing through the transducer so in this case it doesn't matter what current or voltage the transducer draws from the power supply)

am i correct?
 

ericgibbs

Joined Jan 29, 2010
16,015
hi Wolf,
The transducer in post #10 is NOT suitable for the 40kHz drive.

E
Ultrasonic Level Sensor 0-3 Metre Range

4-20mA (2 wire) - 12V DC Power
Accuracy +/- 0.5% F.S
300mm Deadband
Beam Angle 15º
IP67 Rating (IP68 Optional)
Operating Temp 0-50 ºC
M68x2 mm Thread
38K±10Khz Operating Frequency
PP Housing Construction
0.5M Flying Lead

Alternative Outputs on request: 0-5V,0-10V,0-20mA,4-20mA(3-wire),RS485
 

Danko

Joined Nov 22, 2017
1,398
May logic is ( by using the transistor to connect & disconnect the ground lead to the transducer
No current or voltage will be passing through the transducer so in this case it doesn't matter what current or voltage the transducer draws from the power supply)
So you are saying that this 2N2222 transistor is a suitable one?
Yes, it is suitable for 40 kHz, no current, no voltage.
3-an arduino generating 40khz signal @ maximum voltage 5v
Resistor R1 value changed because of connection to Arduino.
Are you using a simulator? What is it?
Simulator LTspice. Download from:
https://www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html
2022.08.03 21-59-41.png
 

MisterBill2

Joined Jan 23, 2018
12,704
The device is an analog output distance measuring system.
That is totally different from an ultrasonic transducer. Others have mentioned that but evidently been ignored.
So far all of the circuits shown will lead to the damage and destruction of a rather expensive item.
So as a fist step in getting a bit of worthwhile advice, let us know what the goal is intended for using some sort of ultrasonic device. Until that information is given, the only good advice is to STOP!!

It appears that the TS, claiming to be a "maker", does not understand any of the comments about the device not being what they wish it to be.
 
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