Hi all, I hope someone out there can help me, as I'm only a once in a few years electronic project builder I don't really know what's out there.
What I'm looking for is a square wave signal generator with adjustable frequency.

I've seen a few out there that are real cheap and have a nice little display on them but the big problem with those is they have push buttons for adjusting the pwm and frequency, what I'm looking for it something very similar but with potentiometers for adjustment

Thanks

 

Are you looking for a signal generator or a small project board that can generate square waves? What frequency range are you looking for? Up to 2 MHz or 20MHz? 200 MHz? or 20 kHz? What is your budget ?

 

A small cheap analog signal generator module (ebay) probably will not have things like a frequency meter built in? Search for projects and kits based on the 8038 function generator IC.

ak

 

Hi all, I hope someone out there can help me, as I'm only a once in a few years electronic project builder I don't really know what's out there.
What I'm looking for is a square wave signal generator with adjustable frequency.

I've seen a few out there that are real cheap and have a nice little display on them but the big problem with those is they have push buttons for adjusting the pwm and frequency, what I'm looking for it something very similar but with potentiometers for adjustment

Thanks

You could just replace the pusbutton with a rotary switch. These are widely used in car radios and probably lots of other places, to give you that pot feel while giving a digital output.

 

If you stated your purpose for having a square wave generator we could supply better advice.
For the moment, here are some specifications you could provide:

Frequency range, e.g. 0 to 1MHz
Duty Cycle - would 50% be sufficient?
Amplitude - would fixed 5V be sufficient?
DC Offset - would fixed 0-5V output be sufficient or does the wave have to be adjusted to go negative?

For less than US$1 you can scramble together a 555-timer circuit or you can buy it pre-assembled off ebay.

 

What I'm looking for is something like these

http://www.icstation.com/mobile/sig...adjustable-module-display-150khz-p-12477.html

http://www.icstation.com/mobile/adj...le-channel-pulse-frequency-150khz-p-9668.html

But with pot instead of switched, maybe I could get some type of rotary switch if they exist, where its spring loaded to center off position, turning anti clockwise would be down and clockwise would be up, I've no idea what this sort of switch is called?

As for budget, I don't want to spend 100's, it to control a 80 amp dc motor speed controller, the controller does have a pot on it for pwm / motor speed but with fixed frequency of 20khz, it's also got a connector for external pwm and frequency control that I hope I can use, the manufacturer states that the pwm and frequency in (on the external control connectors) is the same as out

I'd need adjustable pwm from 0 to 100 and also, if poss a very wide range of frequency

Thanks

 

I don't want to spend 100's, it to control a 80 amp dc motor speed controller, the controller does have a pot on it for pwm / motor speed but with fixed frequency of 20khz,

There is a reason that most motor controllers use around 20kHz. To keep the motor quiet. Anything too much lower in frequency makes the switching audible due to vibration of the motor lamination's and other things in the circuit.

 

Ah, so. You want to control the speed of a high power DC motor. What you need is a DC motor controller, not a square wave generator.

 

I've got the controller, I just need some input for it

Thanks

 

http://www.icstation.com/ne555-mult...uare-triangle-sine-sawtooth-wave-p-10879.html

 

I can't see why you would want a PWM frequency above 20kHz. The higher the frequency the more critical the circuit build quality would be and the harder it would be to keep switching losses (generated heat) low. Below 20kHz you could get noise problems, as mentioned above.

 

Let's qualify "Noise". Audible.

 

You could just replace the pusbutton with a rotary switch. These are widely used in car radios and probably lots of other places, to give you that pot feel while giving a digital output.

Thanks all, I've found what I was looking for, a cheap $3 generator with lcd.
I'm not to worried about noise as this is only a test rig and will only be used for max 40 seconds on each motor.

I now need to find the rotary switches that that Weyneh mentioned above, any idea what they are called?

Thanks Again

 

I now need to find the rotary switches that that Weyneh mentioned above, any idea what they are called?

This should get you started.
https://www.mouser.com/ProductDetai...MHTMhaKzSCPd1ulfSDMW2Eqmldi9hTQEaAqFdEALw_wcB

 

Would this be correct, assuming the switches on the signal generator share a common ground ?




Sorry for the bad drawing, The little squares are the existing up / down micro switches on the signal generator, I can leave those on and just solder to the edge connection if there is room



Thanks

 

Would this be correct...

I've never actually used one, so I'm reluctant to comment. It looks right, but the devil is in the details.

 

Im waiting for the sig gen, should be here in a month or so, ordered from China, once thats arrived I'll check switches to make sure they'e got a common ground, if so I'll order a couple of encoders and see what happens

Thanks again to ALL for all the help

 

Would this be correct, assuming the switches on the signal generator share a common ground ?


View attachment 143453

Sorry for the bad drawing, The little squares are the existing up / down micro switches on the signal generator, I can leave those on and just solder to the edge connection if there is room

View attachment 143454

Thanks

Ive tried this and it dont work, connecting one side works perfect but when both side are connected its trying to switch both ways, up and down, back to the drawing board !

Thanks

 

Link to the sig gen you decided to use?

ak