Question about a circuit using a 555 timer

AI Thread Summary
When the potentiometer in the 555 timer circuit is turned down to zero resistance, the capacitor discharges rapidly, resulting in a mostly high output with a very brief low time. If resistance is completely eliminated, the output could remain high continuously, risking damage to the internal transistor responsible for discharging the capacitor, particularly with larger electrolytic capacitors. A user reported issues with their 555 timer not pulsing correctly, despite checking connections and configurations for an astable mode at 6.5 Hz. Initially, the timer overheated when connected improperly, but after adjusting the resistance, it operated at 5V without overheating. The user suspects either a damaged timer or incorrect pin connections, prompting a request for further troubleshooting assistance.
line2
Messages
2
Reaction score
0
Here's the drawn circuit: http://imgur.com/DGo9M.png

R1 is 10k Ohm resistor
Pot is a 100k Ohm potentiometer
C is 1.0uF Electrolytic Capacitor

My question is, what happens when the potentiometer is turned down to 0 resistance? Would the circuit fry?

thanks
 
Engineering news on Phys.org
Pin 7 discharges the capacitor after it has fully charged. So, if you made the resistor almost zero, the capacitor would discharge very quickly.

This produces an output that is mostly high but with a very short low time.

If you could make the resistance zero, the output would stay high all the time but there is a risk that the transistor that discharges the capacitor (inside the chip) could get damaged, especially if a large electrolytic capacitor was used.
 
problem with my HA17 555 timer

i recently bought my 555 timer and i simply can't get it to pulse. I flick on the switch and i get my buzzer to work that is connected to the output but i don't hear it turn off and on. I set my configuration as astable 6.5 Hz. i checked all my connections and everything seems right. However during my first run, i connected my timer circuit parallel to 1k that was instead of two 1k connected with source along with 30 ohms the circuit (that gave off 9v 8mA). And during my first 2 runs my timer was heating up really fast. After adding another 1k to the source (as the pic) i was able to get 5V and then it didn't heat up. I even checked my simulation with multisim and despite of that i don't get any pulse (the buzzer jus keeps going and no beep).

I am thinking its either i burned my timer or i got the pinning wrong. Check both my image files to see i am doing anything wrong. Btw 9V with 30 ohms in series depicts my adaptor that gives off 9V with 300 mA

Download file from link below.


http://squadinvenire.uuuq.com/555_timer.rar
 
Last edited by a moderator:
Hey guys. I have a question related to electricity and alternating current. Say an alien fictional society developed electricity, and settled on a standard like 73V AC current at 46 Hz. How would appliances be designed, and what impact would the lower frequency and voltage have on transformers, wiring, TVs, computers, LEDs, motors, and heating, assuming the laws of physics and technology are the same as on Earth?
I used to be an HVAC technician. One time I had a service call in which there was no power to the thermostat. The thermostat did not have power because the fuse in the air handler was blown. The fuse in the air handler was blown because there was a low voltage short. The rubber coating on one of the thermostat wires was chewed off by a rodent. The exposed metal in the thermostat wire was touching the metal cabinet of the air handler. This was a low voltage short. This low voltage...
Thread 'Electromagnet magnetic field issue'
Hi Guys We are a bunch a mechanical engineers trying to build a simple electromagnet. Our design is based on a very similar magnet. However, our version is about 10 times less magnetic and we are wondering why. Our coil has exactly same length, same number of layers and turns. What is possibly wrong? PIN and bracket are made of iron and are in electrical contact, exactly like the reference design. Any help will be appreciated. Thanks. edit: even same wire diameter and coil was wounded by a...
Back
Top