boosting output of oscillator

Thread Starter

3dchipmaker

Joined Jul 15, 2006
23
i would like to know how to boost output voltage of an oscillator and still maintain 30 pulses per second.using a 12 v stage or if someone knows a better schematic than 555 timer
 

Thread Starter

3dchipmaker

Joined Jul 15, 2006
23
Thanks For Your Reply.
The Problem Is That When Assembled The Out Put Is 6v I Would Like It To Be As Close To 12v As Possible And Still Maintain Pulse Rate.
 

hgmjr

Joined Jan 28, 2005
9,029
3dchipmaker said:
Thanks For Your Reply.
The Problem Is That When Assembled The Out Put Is 6v I Would Like It To Be As Close To 12v As Possible And Still Maintain Pulse Rate.
When you measure the output of the circuit to be 6v, do you have the output connected to anything other than a meter or an oscilloscope?

The reason for my question is that maybe your load is causing your reading to be low. Keep in mind that the output impedance of the driver shown in your attached schematic is 100 ohms. There is also an LED in series with the output. If you are measuring your 6v signal across whatever load you are connected to, then if the load is around 180 ohms or so then the output voltage across the load would be pretty close to 6v.

hgmjr
 

Thread Starter

3dchipmaker

Joined Jul 15, 2006
23
Thanks For Your Reply,

Voltage Going Into Collector On Transistor Is 12v. Voltage On Base Is 6v. But Emitter Voltage Is 6v Before Resistor And Led. Is There Any Way To Ramp Up Voltage As Close To 12v Rail As Possible
At Emitter Discharge Without Changing Frequency
 

hgmjr

Joined Jan 28, 2005
9,029
The circuit as shown in your schematic should produce a signal swing at the emitter of transistor between 0V and 11.3V without any problem.

Is it possible that you have accidentally installed the transistor so that the emitter and the collector have been swapped? This could cause your problem. To check that the 555 output is swinging between 0V and 12V, you can temporarily disconnect the 555 from the transistor and check the output at pin 3 of the 555 without any load. If the 555 is swinging between 0V and 12V then the problem most likely resides in the way the transistor is connected up.

hgmjr
 

Thread Starter

3dchipmaker

Joined Jul 15, 2006
23
thanks for your help!!
i have another schematic that puts out about what i want and has a good sharp pulse.i need to tune the pulse rate. it is in the ballpark but i want 30 pulses per second. can i attach a pot to this circuit to control pulserate and if so where?
 

Attachments

pebe

Joined Oct 11, 2004
626
3dchipmaker said:
attached is schematic

thanks,
3d
If you are using the standard bipolar 555, its output is fed from the 12v rail via two NPN transistors connected as a Darlington pair. That, together with your external transistor, gives 3 x 0.7v drops from the rail. So your output cannot exceed 9.9V even with a high value resistive load.
 

Thread Starter

3dchipmaker

Joined Jul 15, 2006
23
thanks for your reply!

what i cant understand is why the output voltage is 6v. i guess that is how circuit is designed because they are feeding base of transistor whith the output at pin 3
 

Thread Starter

3dchipmaker

Joined Jul 15, 2006
23
thanks for your reply!

yes i removed transistor and voltage was 6v and thats what runs base on transistor pin 3 on 555. i tried everything i could think of before this forum.
swapping testing disconnecting reconnecting for 3 weeks.i just know the basics of electronics i guess what i really need is a bare bones oscillating circuit that i can get as close to 12v output and pulse 30 times a second with 12v input.does anyone know of a schematic?

thanks for all of your help!
3d
 

Thread Starter

3dchipmaker

Joined Jul 15, 2006
23
thanks for reply,
im using a variable dc power supply and its putting out 12vdc i tested with multimeter.attached is assembly i assembled exactly like assembly shows i built 4 of these and everyone works the same with the same output levels maybe its a problem with assmbly can you check and see if assembly is correct to schematic it looked like to me but i just know basics

thanks,
3d
 

Attachments

hgmjr

Joined Jan 28, 2005
9,029
3dchipmaker said:
thanks for your help!!
i have another schematic that puts out about what i want and has a good sharp pulse.i need to tune the pulse rate. it is in the ballpark but i want 30 pulses per second. can i attach a pot to this circuit to control pulserate and if so where?
I think you need to connect pin 7 of your 555 to the junction of the pot and the feedback resistor R2.

http://www.allaboutcircuits.com/vol_6/chpt_6/7.html is a link to an astable 555 oscillator in the AAC tutorial section that shows how the discharge pin should be connected.

Without pin 7 (discharge) connected up, the 555 will not oscillate properly since there is nothing to discharge the capacitor to start the charge cycle over.

Your schematic seems not to show pin 7 being connected at all.

hgmjr
 

pebe

Joined Oct 11, 2004
626
JoeJester said:
3D,

Where did you get that original schematic in your first posting? It also doesn't show pin 7 connected.
The original circuit shown for the 555 will work OK. It does not need the discharge pin connected. It is an astable oscillator with a unity mark-space ratio. The problem, as I said before, is that the output will not go to the +ve rail.

Wiring the driver transistor as in the attached circuit will ensure that the transistor is switched hard on and off and the output will swing between about 0.3V and 12V. The fact that the transistor inverts the signal doesn't matter.
 
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