This circuit, can it be minimized?

[Addohm]

I found this here, and began to look at it thoroughly.

**broken link removed**

It seems to me that this circuit does not need to use a IC 4001. You can just make two transistor OR gates and get the same results. I would like to make this much smaller, and could use some help on it. I've been out of the electronics field for 9 years or so, so I am very rusty

This unit is used on an electric drum set. The drum brain sends ~3.3v to the single foot pedal, and pressing the foot pedal makes a switch to complete that circuit.

The point of creating this, is to be able to use two foot pedals on the same circuit, but the trick is to be able to use either pedal, reguardless if the other pedal is up or down.

To make this circuit currently, I can do it on about 1.5x1.5" 2 layer PCB, but if I can shrink it, I would like to. I was thinking that the chip itself can be eliminated, but maybe my own logic is too rusty to see where I may be wrong.

Thanks,

Adam

 

[ericgibbs]

hi,
The circuit you posted give a 'timed' single pulse output whenever a input closure occurs.

A transistor OR wouldnt do that, it would be an output for as long as an input is closed.

OK.?

 

[Addohm]

Okay.

Still, is there a better way to build this to make it smaller then it's current size?

 

[ericgibbs]

Okay.

Still, is there a better way to build this to make it smaller then it's current size?

You could consider a SMT surface mounted component [ for the ic]

 

[Addohm]

You could consider a SMT surface mounted component [ for the ic]

I've never mounted an SMT before, nor have I ever seen one done by hand

Maybe you can help me with my PCB layout? I'm not really all that good at laying it out from schematic to pcb.

 

[flat5]

Here is one way to lay out your project.
It's a start, anyway.

It's a one sided board for simplicity. Two jumpers are required.
It is a terrible layout if you are going to use point to point wiring.

 

[KMoffett]

Why is it that no one seems to try and reduce the foot print of a thru-hole PCB by mounting axial components...resistors, diodes, capacitors...on end. Why don't PCB CAD libraries don't include them? OK, machine-stuffing doesn't lend itself to doing that. I use PCBExpress, and created a whole series of components for vertical mounting. I even created diode and axial electrolytic capacitor packages with a choice of either polarity down, for tighter spacing.

Just n observation.

Ken

 

[dknguyen]

Possibly because of shorts from components being knocked back from mishandling? More lilkely just because it looks nicer.

 

[KMoffett]

Possibly because of shorts from components being knocked back from mishandling? More lilkely just because it looks nicer.

I agree the horizontal mounting is more rugged. The reason for the choice of polarities on the vertical foot prints was so that I could arrange the exposed leads in a position that would not place them adjacent to other exposed leads.

Just another option, if you need it.

Ken

 

[ericgibbs]

I agree the horizontal mounting is more rugged. The reason for the choice of polarities on the vertical foot prints was so that I could arrange the exposed leads in a position that would not place them adjacent to other exposed leads.

Just another option, if you need it.

Ken

hi Ken,
One reason I use them, they are ideal for scope/meter probes [bent the right way]

 

[KMoffett]

hi Ken,
One reason I use them, they are ideal for scope/meter probes [bent the right way]

Yup...forgot to mention that. I pick the "wire-side-up", when I can, for test points too.

Ken

 

[Ubergeek63]

I found this here, and began to look at it thoroughly.

It seems to me that this circuit does not need to use a IC 4001. You can just make two transistor OR gates and get the same results. I would like to make this much smaller, and could use some help on it. I've been out of the electronics field for 9 years or so, so I am very rusty

This unit is used on an electric drum set. The drum brain sends ~3.3v to the single foot pedal, and pressing the foot pedal makes a switch to complete that circuit.

The point of creating this, is to be able to use two foot pedals on the same circuit, but the trick is to be able to use either pedal, reguardless if the other pedal is up or down.

To make this circuit currently, I can do it on about 1.5x1.5" 2 layer PCB, but if I can shrink it, I would like to. I was thinking that the chip itself can be eliminated, but maybe my own logic is too rusty to see where I may be wrong.

Thanks,

Adam

A friend here at work just built that. He was originally asking me about it because of parts availability. There is a problem with metastability and shoot through with that circuit that I only know about because he asked me to look into alternate parts.

My suggestion was a 74HC132 and swap the polarities. HCs are not static sensitive compared to CD4000s and having schmidt inputs takes care of the rise time fall time specs. You need to swap polarities because the HC132 is a NAND instead of a NOR.

Exceeding the rise and fall time specs can cause logic to either draw excessive current or oscillate, which also draws excess current.

 

[Addohm]

This is the prototype I put together with expressPCB. Can someone verify that it is correct for me? I'd hate to go burning this and find out it's wrong

P.S. I modified it a bit. R6 is a 330k resister, L1 is an ultra bright LED. I also changed the power source to a USB port, which changes the +3v to +5v.

Bottom Layer
**broken link removed**

Top Layer
**broken link removed**

Both Layers with Part ID's
**broken link removed**

Color Traces with Components
**broken link removed**

Thanks in advance!

Adam

 

[ericgibbs]

P.S. I modified it a bit. R6 is a 330k resister, L1 is an ultra bright LED. I also changed the power source to a USB port, which changes the +3v to +5v.

hi,

Using a 330K for R6 will not drive the output transistor hard enough.

Where is L1 on the original circuit.

The +3V to +5V will have little effect on the circuit.

 

[KMoffett]

Adam,

Can you zip the .sch and .pcb files and post it?

Ken

 

[Addohm]

hi,

Using a 330K for R6 will not drive the output transistor hard enough.

Where is L1 on the original circuit.

The +3V to +5V will have little effect on the circuit.

As I said, I modified the original circuit to include these components. L1 and R6 aren't in the original circuit. R6 doesn't have any effect on Q1 (NPN Transistor), that I can see.

Adam,

Can you zip the .sch and .pcb files and post it?

Ken

I can post the .pcb file, I don't have an .sch though, I just jumped in to ExPCB and drew it up

Thanks,

Adam

 

[Addohm]

I take it you don't see any problems with that circuit?

My suggestion was a 74HC132 and swap the polarities. HCs are not static sensitive compared to CD4000s and having schmidt inputs takes care of the rise time fall time specs. You need to swap polarities because the HC132 is a NAND instead of a NOR.

A Quad-NAND wouldn't work really without redesigning the whole circuit. Even then, it really wont work as you would still require a "one foot on, one foot off" scenario.

I have been thinking of adding a schmitt trigger though, as unwanted "kicks" are....unwanted But at 5v I really shouldn't have too many of those. SN74HC7002N would take care of it anyways, I'll add it in once in once I have a final prototype.

Both of my kick pedals use reed switches, so it is very possible to have double kicks due to contact bounce and\or vibration. Perhaps I should use a different switch as well.

 

[ericgibbs]

hi,
Please dont keep editing your posts as it makes our replies out of context.

 

[Addohm]

Haha, sorry, I was looking through Mouser. I wasn't sure if Quad-NOR Schmitt Trigger IC's existed

I also decided to change the switches on my kick pedals. I will probably use paddle or push button. Paddle is more likely though, I can use a tapered trigger plate and eliminate doubles all together.

 

[Addohm]

Oh, I'll be adding a push button toggle switch also for the power. What good is an LED as an indicator, if you can't lazily turn off the power