Ultrasonic circuit explination

[Corky]

just as an output load ive used a 68 Ω aswell no difference

 

[ericgibbs]

Morning Dale,
I'm checking your B/B photo, which circuit diagram are you using.?
E

 

[Corky]

i was going to set a 555 timer up on its own first get th 40khz output then look at the transmitter receiver, but the output of the 555 is only 20mv and im not sure why ill probably use the latest one to go of
cheers

 

[ericgibbs]

How are you measuring the output.?

If its a DVM you will not get an accurate reading with a narrow pulse.?

 

[Corky]

yer im using a DVM i can only use an oscilliscope at college on tuesdays :/

i might be getting one tonight though depending if someone gets back in touch, so does that circuit look ok from a layout pov?

 

[ericgibbs]

To check if your 555 is running, add a 10uF cap across the 0.01uF, connect a 470R resistor from pin #3 to an LED to 0V, it should flash.

EDIT:
make that a 100uF not a 10uF

BTW: the 555 is running at 35KHz in your original circuit.

 

[Corky]

ok im at work at the moment so i will have to check when im home, ill let you know how i get on,

i will have to re-calculate the values i need as i thaught it would be around 40KHz :/

no worries easy fixes

Cheers E

 

[Corky]

do you mean my BB is 35khz or the original on this post?

re checked and its 40KHz

Cheers

 

[Corky]

.

 

[Corky]

this is really killing me now as i get nothing lol, i still think its the 555 because it gets really hot but i cant test untill tuesday when i can use a scope

any ovious things guys?
ive bridged the bottom gap for voltage and still nothing btw

any advisae will be appreciated cheers for sticking with it

 

[audioguru]

Why are your resistors HUGE? 1W? I use 1/4W resistors.
EVERY electronic circuit and sometimes every IC should have a power supply bypass capacitor. 0.1uF is good. It prevents an IC from oscillating at a high frequency that makes it hot. Your circuit is missing one or two. It should be VERY close to the power supply pins of the IC.

All the 555 circuits in this thread use feedback from pin 3 to pins 2 and 6 so the output is a squarewave. Your 555 circuit is different and uses feedback from pin 7 which might produce narrow pulses instead of a squarewave.

What is your supply voltage and what is the part number of your 555 so we can see if it is a Cmos (max supply about 12V) or ordinary 555 (max supply about 15V)?

 

[ericgibbs]

hi dale,
Use your DVM and tell us what the voltage is on EVERY pin of the 555.
E

 

[Corky]

yer 1w i think, i know its overkill but it saves buying several types of thee same resistance, am i wrong in thinking this wouldnt make a difference?

power supply bypass cap? im not sure what this is?

i was going by a tutorial on how to make a square wave at this frequency online i hadnt noticed it was different tbh

NE555
1-0v
2-4.55v
3-0.02v
4-8.19v
5-5.55v
6-4.55v
7-4.56v
8-8.14v

vcc- 8.36v

cheers guys i changed the cap on pin 5 to 15pf and the 555 doesnt get as hot now, this might be usefull

the output voltage is still low though

Thanks again guys

 

[audioguru]

A power supply bypass capacitor is recommended in the datasheet of the 555. Connect a 0.1uF ceramic capacitor with short leads between pin 8 (Vcc) and pin 1 (Gnd) as close to the pins as is possible.
The datasheet shows a 0.01uF (10,000pF) capacitor from pin 5 to pin 1 (Gnd).

Measure the resistance of the Tx transducer (disconnected from the circuit). If it is a piezo one then its resistance should be infinity.

 

[ericgibbs]

hi dale,
Look at this 555 Tool I posted sometime ago.
https://www.electro-tech-online.com/tools/IC555V2T2.php

E

 

[Corky]

cheers again guys, ill check this all when im home,

eric your calculator is really good ive not seen one like that before

ill keep you updated