Here is another choice, with very low parts count because it uses a PIC;

http://romanblack.com/onesec/SineDDS.htm

It is crystal locked, so the frequencies are very stable, and the frequencies are in exact decimal Hz steps, like 10Hz, 20Hz, 1000Hz etc. (Total range 5Hz to 20kHz).

The new firmware (see page bottom) now lets you select sine/square/triangle/sawtooth.

 

Hi Dr. killjoy,

Strangely enough I've just built a function generator based on the ICL 8038, at least breadboarded it out.... It works really well, just some minor issues to iron out. Rather than hijack this thread I'll start a new one ;-)

I built #1 the Velleman version and its rubbish, the Dave Jones version is probably quite good, but the chip is exxxxxxpensive, the last one just doesn't hack it really.

Anyway, I've got a spare ICL 8038 chip, PM me your address and I'll stick it the post tomorrow! If you want that is. I used this design here.

All the best Steve.

What did you use for a power supply or how did you power it ??

Or can anyone please tell me what does it mean with 6-0-6 coming of the secondarys of the transformer???

 

Today I did some reading and found some information out about transformers...


I found a couple but was not sure if these are going to work and would like a second opinion because I found one at RadioShack with spec's (12.6V CT 1.2A Standard Center Tap Transformer with leads) ,but was not sure the extra .3 volts would make a difference in the circuit???

 

Hi Drkilljoy,

The transformer you posted should be fine, however a 500ma transformer, will probably be less expensive. I assume that you've worked out that 6-0-6 means a centre tapped transformer with two 6 volt secondaries. I used a bench supply which is variable, but there are many ways to create a dual supply.
The power supply in the schematic uses 78/79 series linear regulators to limit and maintain a constant voltage. They need about 2 volts more in than out to function correctly. A few volts more wont hurt at all, however voltage in should not be too high since the extra voltage that is regulated out will be given off as heat. Also remember that rectification of AC voltage produces a higher DC voltage (RMS).

 

I am looking for Generator for my small office requirement is very limited just 15-20 system,3 AC and 10-20 CFL bulbs. Recommend some low cost and low maintenance Generator.

 

Hi Drkilljoy,

The transformer you posted should be fine, however a 500ma transformer, will probably be less expensive. I assume that you've worked out that 6-0-6 means a centre tapped transformer with two 6 volt secondaries. I used a bench supply which is variable, but there are many ways to create a dual supply.
The power supply in the schematic uses 78/79 series linear regulators to limit and maintain a constant voltage. They need about 2 volts more in than out to function correctly. A few volts more wont hurt at all, however voltage in should not be too high since the extra voltage that is regulated out will be given off as heat. Also remember that rectification of AC voltage produces a higher DC voltage (RMS).

Yeah I figure out what the center taps means lol ... But I tried finding a transformer all around and found out that radio shack was still the cheapest option and maybe you guys know where I could get one for cheaper ?? Also I did think think about build a dual rail power supply but was not sure where to even start so just stuck with what I know ..

I am looking for Generator for my small office requirement is very limited just 15-20 system,3 AC and 10-20 CFL bulbs. Recommend some low cost and low maintenance Generator.

LOL This is a function generator not a power generator and please delete post and post up new thread for yourself...

 

Today I did some reading and found some information out about transformers...

and

Also I did think think about build a dual rail power supply but was not sure where to even start so just stuck with what I know ..

Yes please note that messing around with mains input voltages requires special attention and this site does not promote poor practice in this area. So if you do not know how to make a safe mains based supply, find someone who does to help and check over what you do.

 

Yes please note that messing around with mains input voltages requires special attention and this site does not promote poor practice in this area. So if you do not know how to make a safe mains based supply, find someone who does to help and check over what you do.

I don't mind playing around with dc voltage but ac voltage Just scares me... Also I have no one to help me so I am flying solo and that's why I come here for help and ask questions....

 

Here is a 12.6vct, 200mA transformer from Jameco for US $6.95. Is this a better deal than the RS part?

 

Here is a 12.6vct, 200mA transformer from Jameco for US $6.95. Is this a better deal than the RS part?

It won't work I think because it doesn't have enough amps ....Here is what I can get at my local radio shack...

http://www.radioshack.com/product/i...3732&filterName=Type&filterValue=Transformers
RadioShack® 12V CT 450mA Std Chassis-Mount Xformer w/ Leads


$7.49

http://www.radioshack.com/product/i...2700&filterName=Type&filterValue=Transformers
12.6V CT 1.2A Standard Center Tap Transformer with leads

$10.49

 

That first part is pretty nice, but a 100mA transformer would be more than enough. The 8038 draws 20mA max. The LF351 draws 3.4mA max.
If you have plenty of outlets, you could pick up a couple of junk 9V wall warts at the Goodwill/whatever store. These will take the place of the transformer and the rectifiers.

 

Hey,

Using a wall wart is not a bad idea, I thought about using one with an ICL 7660 voltage converter -- couple of caps and an IC and away you go.......

Datasheet below.

 

That first part is pretty nice, but a 100mA transformer would be more than enough. The 8038 draws 20mA max. The LF351 draws 3.4mA max.
If you have plenty of outlets, you could pick up a couple of junk 9V wall warts at the Goodwill/whatever store. These will take the place of the transformer and the rectifiers.

So how would you go about creating a negative dc rail with wall warts ????

Hey,

Using a wall wart is not a bad idea, I thought about using one with an ICL 7660 voltage converter -- couple of caps and an IC and away you go.......

Datasheet below.

So how would you go about creating a negative dc rail with wall warts ????
Will have to check out the 7660 later when I have more time and thanks for the input guys .

 

So how would you go about creating a negative dc rail with wall warts ????

So how would you go about creating a negative dc rail with wall warts ????
Will have to check out the 7660 later when I have more time and thanks for the input guys .

Wall warts have a +output and a -output. For the positive rail, connect the -output to circuit ground. For the negative rail, connect the +output to circuit ground.