Please check the schematic circuit

[manie]

Someone please cast a beady eye over this for any faults/mistakes. PWM from 3x 08M's for the three freq's.

The DIP switch will set the input pins high/low for coding a different PWM frequency and/or Duty cycle. (I may just add a 5K preset pot on leg 6 for ADC reading to set/alter the duty cycle.) The TC4420 drives an IRF540N Mosfet.

Power supply both 5V and 12V from regulated source. Each 08M can be programmed separately for different settings etc.

As always, any help appreciated..
Thanks
Manie

 

[eclectic]

Manie.

A very quick reply.

Please make the schematic BIGGER!
(Or INCREASE the file-size)

Some of us are mildly presbyopic.


e

 

[manie]

View attachment 3316Is this any better ? I tried saving at 200%.... let me know.

Edit:
The DIP switch at left seems to have been lost. Its connected via 470R's to the input pins. The download circuit is also slightly cut... I'll see what I can do if anything, to improve.
Manie

Here is another image

 

[eclectic]

MUCH better definition, but parts are chopped off. :-(
What does it look like when YOU download it?

Possibly 100% would be best.

e

 

[manie]

New image loaded, OK now....

 

[Andrew Cowan]

You could add a 100uF across the power lines.

A

 

[MPep]

DIP switch common needs to go somewhere (high ie 5V). The bottom switch...what is it for?
As Andrew mentions, a large electrolytic capactir needs to be on the circuit somewhere also. And yes, this despite the fact that you are using a regulated power supply.

 

[sghioto]

Looks like the bottom dip switch is used as a master for routing the commons on the other three dip switches to 5 volts. I'm assuming the intent was to bring all inputs low with the master switch open, set the three inputs as needed then turn the master back on.

Steve G.

 

[hippy]

The programming jack is wired wrongly for a standard Rev-Ed download cable -

Tip - 0V
Ring - TX from PC to 10K/22K
Sleeve - RX to PC from 08M leg 7

The 470R's for the switches could be omitted.

 

[manie]

Thanks guys, changes made. Steve, you're right on, bottom switch is the master on/off for changes.

100uF's actually on the power supply module, but I've added them here for clarity.

Is the Jack for the download cable correct this way ?

The 470R's were included just as "current limiting" resistors. If they are not required then out they go..

Manie

 

[hippy]

Is the Jack for the download cable correct this way ?

No ...

Tip - 0V
Ring - TX from PC to 10K/22K
Sleeve - RX to PC from 08M leg 7

 

[tiscando]

To be more specific: I think Rx and Tx is reversed.

If you prefer to have short-prevention resistors before the inputs that can be outputs, then 270R or 330R resistors can be used. Connect it like in the diagram.

 

[manie]

Thanks Hippy. I will draw up a schematic component to represent the actual stereo socket from Rev-Ed and place that in the Library. That way I'll get the pin connections right.

Tiscando, thanks also, I hace 3x 10k pull-down R's on two of the input pins and on the PWM output, leg 5. Leg 6 I've changed to an analogue input so I've removed the pull-down there.

I had two types of presensitised PCB's. The white background board is the "VR" marked board from Rev-Ed. It worked really well but is MUCH MORE sensitive to UV than the dark board. So that meant one board messed up to determine exposure. The second one was spot-on and it etched really well. I like it. Attached is an image of the two boards made today. The photo resist is still there, I'll remove it just prior to populating with components.

As always your comments and suggestions welcome.
PS: I'm still waiting for my BB from the East....
Manie

 

[hippy]

Leg 6 I've changed to an analogue input so I've removed the pull-down there.

You'll probably want to put it back in otherwise you have a floating analogue input when the switch is open. There's not really a lot to be gained using analogue over digital when reading a switch.

If you want to minimise components, enable the internal weak pull-ups ( by poking SFR's ) and have the DIL switches to 0V. No resistors at all required for your switch inputs.

 

[manie]

Hippy: The schematic must be updated (time permitting). Leg 6 will be a "true' analogue input, +5V---5k var---470R----0V, with the wiper feeding leg 6, so it won't be floating. So instead of just two choices(high/low), leg 6 can read 0--255 steps (say maybe 10 represented values calculated), giving me much finer control on setting Duty Cycle. The other two pins from the DIP switch will give me four choices to set frequency(+-42KHz to +-30KHz) which is OK. The next 08M down (exact same circuit), handles the "other" frequencies(28KHz to 16KHz) with analogue setting on Duty Cycle also, and the third 08M down does the same for 14KHz to +- 8KHz. The reason for the first thread about 3 PWM frequencies...
Manie
Edit:
Thinking about it now, I should really have changed leg 3 (ADC4) to analogue as well, then I can have "infinite" frequency setting between 42KHz and 28KHz.....