Author Topic: Please help me with this DDs function generator module!!  (Read 2316 times)

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Offline kgavionicsTopic starter

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Please help me with this DDs function generator module!!
« on: June 26, 2017, 03:57:31 am »
hi guys
I bought this small function generator module based on ICL8038 circuit from ebay, but i didn't receive any instruction  how to use it.I searched on internet ,but no luck.My problem i can't get any sinwave output.there are three output pins:
1-SIN/TRG ( common output shared between sin and triangle wave)
2-SQR
3-GROUND
i have the triangle and the square wave, but i don't know how to switch to  the sin wave output.
can someone help me with that please?
thanks in advance
 

Offline MarkF

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Re: Please help me with this DDs function generator module!!
« Reply #1 on: June 26, 2017, 04:42:01 am »
I found this circuit diagram here.
Did you try the switch? It appears to toggle between sin and tri output on  the diagram.
 
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Offline kgavionicsTopic starter

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Re: Please help me with this DDs function generator module!!
« Reply #2 on: June 26, 2017, 06:17:12 am »
thank MarkF for the diagram.
yes indeed i tried the button,but  i get a shape like a triangle wave  with a lower amplitude (see attachment), it's not a sin wave at all .it played with all the pots and jumpers, but no luck .weird problem


« Last Edit: June 26, 2017, 06:47:36 am by kgavionics »
 

Offline Kleinstein

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Re: Please help me with this DDs function generator module!!
« Reply #3 on: June 26, 2017, 04:47:01 pm »
The sine waveform usually needs adjustment. With so many pots, one usually should follow some system with adjusting. The data-sheet for the ICL8038 should be a good start to look at. The first is having a nice symmetric triangle - it looks like the duty cycle is already OK. Than there are still two more pots for the sine adjustment.
 
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Offline kgavionicsTopic starter

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Re: Please help me with this DDs function generator module!!
« Reply #4 on: June 27, 2017, 03:06:09 am »
i tried all the pots with the same result.i gave up on this crappy product.
thanks guys for your help anyways
 

Offline Kleinstein

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Re: Please help me with this DDs function generator module!!
« Reply #5 on: June 27, 2017, 05:15:36 pm »
It looks like they screwed up the sine waveform adjustment. Compared to the circuit in the datasheet they seem to have swapped the pot and fixed resistor for the Adjustment at pin 1.

It looks way worse than with no adjustment. So it might be worth a try and disconnect pin 1. One might remove the pin from the socket or unsolder the pot used for Pin 1.

Just in case the trouble is with the amplifier or switch: the sine signal should be at pin 2 of the ICL8038 and the triangle at pin 3.
 


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