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Author Topic: Cheap Square Wave Generator  (Read 324 times)

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Posts: 152
Got the little square wave gen boards yesterday.  So far it has some issues with upper freq at very low duty cycle. But should do the job for the projects im planning.

$10
1hz to 150kz
Output mirrors input level 3v to 30v
1% to 100% duty

https://youtu.be/BcTDSGTNWMw

Mags
« Last Edit: 2019-02-18, 02:46:43 by Magluvin »
   
Sr. Member
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Posts: 366
Hi Mags,

Thanks for introducing the square wave generator you bought. Would like to ask, when you have time to check the current draw (at say 50 kHz 50% duty and the output is not loaded) from say 12V and 24V. I guess it is in the 10 - 20 mA range or even less but this data is not included in the specifications anywhere I looked at.   

In the meantime I found the same module type with two and 3 outputs (channels as the sellers call them) too. This very likely means the 2 or 3 outputs will have the same frequency you set in as usual but the duty cycle can independently be varied per channels.  At least this is how I understand the ebay offers, see some here (all offers have free shipping and at least 4 week delivery time):

https://www.ebay.com/itm/173285815317   3 channel  US 3.49 

https://www.ebay.com/itm/332862159283   2 channel  US 3.85 and 3 channel US 4.70

https://www.ebay.com/itm/273107868051   1 channel GBP 1.88 LCD and 2 channel GBP 1.42 but with 7 segment LED display

Thanks,
Gyula

   

Full Member
***

Posts: 152
Hi Mags,

Thanks for introducing the square wave generator you bought. Would like to ask, when you have time to check the current draw (at say 50 kHz 50% duty and the output is not loaded) from say 12V and 24V. I guess it is in the 10 - 20 mA range or even less but this data is not included in the specifications anywhere I looked at.   

In the meantime I found the same module type with two and 3 outputs (channels as the sellers call them) too. This very likely means the 2 or 3 outputs will have the same frequency you set in as usual but the duty cycle can independently be varied per channels.  At least this is how I understand the ebay offers, see some here (all offers have free shipping and at least 4 week delivery time):

https://www.ebay.com/itm/173285815317   3 channel  US 3.49 

https://www.ebay.com/itm/332862159283   2 channel  US 3.85 and 3 channel US 4.70

https://www.ebay.com/itm/273107868051   1 channel GBP 1.88 LCD and 2 channel GBP 1.42 but with 7 segment LED display

Thanks,
Gyula

hey Gyula. No problem.

Ill do that input test. I suspect there is a regulating circuit, probably a resistor and zener to run the device at various voltages, so its possible the idle input will rise as the input voltage rises to 30v. Will see. Just fiddled yesterday. Was able to get my bifi to ring a sine at 12.7khz via 1 wire from the gen at 50% Duty. Rung up to near 7v.

Will be trying to drive a mosfet tonight to pulse the Orbon and see how it goes. Then I will wind Brads SS device and give that a go also if all goes well.

Mags
   

Full Member
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Posts: 152
Idle currents...

5v    22.4ma
15v  27ma
30v  33.9ma.

not much more than a typical led. Of which the screen is backlit by a side led under the white plastic to the left of the screen.

Mags
   

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Posts: 1470
Can any of these generators do a 100ns pulse every 2s ?
   
Sr. Member
****

Posts: 366
Idle currents...

5v    22.4ma
15v  27ma
30v  33.9ma.

not much more than a typical led. Of which the screen is backlit by a side led under the white plastic to the left of the screen.

Mags

Hi Mags,

Okay, thanks.  In the meantime I found the PCB side photo of the module and it turns out there is a 1 kOhm resistor labeled as R1 (lower left corner) in the collector of transistor Q1 (upper left corner). This means the 1 KOhm gives an additional load (though not so much) for the supply voltage as Q1 is controlled by the output pulse. The output (labeled as PWM) is the common point of the collector and the 1 kOHm resistor.  So this makes up for the total consumption, in addition to what you said.

For verpies:  here is some review https://www.wanhunglo.com/2018/pwm-pulse-frequency-duty-cycle-adjustable-square-wave-signal-generator-module-whl-43  and the microcontroller is an ST 8S003F3P6

Gyula
   

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Posts: 710
mine are ordered. Will take a couple of weeks to get them.
   

Hero Member
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Posts: 1470
I read it and it cannot do 100ns pulse every 2s.
I think it could with a better firmware...
   

Full Member
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Posts: 152
I read it and it cannot do 100ns pulse every 2s.
I think it could with a better firmware...

Hey Verpies

Its not the greatest. But for some projects and experimentation I find it very useful.  There may be times where we need more than 1 or 2 or 5 gens. Could get expensive otherwise.  And, it is so inexpensive that a budget minded experimenter can afford this and do many things with it.  ;D

Mags
   

Hero Member
*****

Posts: 710
Mine just arrived. Have the alnico mag experiment hooked up so I'll be trying that. How are yours doing Mags?
   
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