• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

problem with 555 output in astable mode

Status
Not open for further replies.

deanmi

New Member
Hello all,

I needed to use a pwm signal to synchronize my data collection in two computers. I used a 555 to generate a PWM signal 50% duty cycle waves at 0.5 Hz. When I checked the output wave on a scope, everything seemed in order! and square waves were stable. However, once I connected the output pin (#3 of 555) to the data acquisition, the output wave was not stable!! It appeared that the output square wave's amplitude being modulated! The frequency is not affected though.

I am sure the load from the data acquistion equipment is causing the change in amplitude. However, using an impedence or a power transistor on the output have not resolved the issue for me!

I would appreciate if someone can help me understand what is really going on! Thanks.
 

Sceadwian

Banned
Post a full schematic of your circuit, a 555 usually has a pretty good current source/sink ability. Without detailed information about your load we can't answer the question any better than you can.
 

deanmi

New Member
Thanks for your reply. I have attached a schematic which is a typical use of 555 in a astable mode. I dont know the load from my acquisition equipment. Thanks.
 

Attachments

Sceadwian

Banned
If you don't know the load of your aquisition equipment we can't help you. I'm sorry but it's that simple. We can't pluck this information out of the air.
 
Last edited:

Torben

Well-Known Member
Thanks for your reply. I have attached a schematic which is a typical use of 555 in a astable mode. I dont know the load from my acquisition equipment. Thanks.
Hi there,

Is that the actual circuit you're using, or just an example one? Most of the members here already know how to do an astable 555 circuit, so if that's just an example then it will not be helpful, unfortunately.

Surely you have a schematic of the circuit you are actually using?


Regards,

Torben
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top