Dear Members,
I need help to redesign a circuit from 20 years ago.
I would like to make it smaller and improve on functionality.
I am however not an electronic engineer, so if someone here can help me out, it would make me a happy man.

I would like to add display and timer-program, swap the 9V battery(ies) with one rechargeable Li-Battery, and fit this into a watch-size case. Am i dreaming?

 

I would like to add display and timer-program, swap the 9V battery(ies) with one rechargeable Li-Battery, and fit this into a watch-size case. Am i dreaming?

Yes. While Apple has demonstrated what you can do inside a watch case if you have lotsa money, I don't think you have enough. In terms of complexity, a better example would be a digital watch. Casio builds hundreds of thousands of them each year and sells them for almost pennies, but development costs run around $500K for each basic mechanism.

The circuit is a reworked version of the Beck blood electrifier. Once you crank up the digital electronics needed for a display and timer, you can add in the 4 Hz oscillator with more firmware. You'll still need an H-bridge driver. Nothing will beat the LM358 for size and cost, so the net savings is one capacitor and one resistor. Next up you'll need an 8:1 boost converter, which is not a very efficient circuit when the source voltage is so low.

Of course it can be done, but once you work up a prototype you'll see the packaging problem.

ak

 

If you get as many items in a SMT format in place of through hole, it will reduct the size considerably, just a little harder to put together.
Max.

 

If you get as many items in a SMT format in place of through hole, it will reduct the size considerably, just a little harder to put together.
Max.

yes. SMT is a must. Im not sure though if all of the components i used when i made my bords manually are available in a smaller size. The pot-meter has to be changed for buttons instead. That means changes to the circuit.

 

Yes. While Apple has demonstrated what you can do inside a watch case if you have lotsa money, I don't think you have enough. In terms of complexity, a better example would be a digital watch. Casio builds hundreds of thousands of them each year and sells them for almost pennies, but development costs run around $500K for each basic mechanism.

The circuit is a reworked version of the Beck blood electrifier. Once you crank up the digital electronics needed for a display and timer, you can add in the 4 Hz oscillator with more firmware. You'll still need an H-bridge driver. Nothing will beat the LM358 for size and cost, so the net savings is one capacitor and one resistor. Next up you'll need an 8:1 boost converter, which is not a very efficient circuit when the source voltage is so low.

Of course it can be done, but once you work up a prototype you'll see the packaging problem.

ak

 

Yes. While Apple has demonstrated what you can do inside a watch case if you have lotsa money, I don't think you have enough. In terms of complexity, a better example would be a digital watch. Casio builds hundreds of thousands of them each year and sells them for almost pennies, but development costs run around $500K for each basic mechanism.

The circuit is a reworked version of the Beck blood electrifier. Once you crank up the digital electronics needed for a display and timer, you can add in the 4 Hz oscillator with more firmware. You'll still need an H-bridge driver. Nothing will beat the LM358 for size and cost, so the net savings is one capacitor and one resistor. Next up you'll need an 8:1 boost converter, which is not a very efficient circuit when the source voltage is so low.
Of course it can be done, but once you work up a prototype you'll see the packaging problem.

ak

Thanks, yeah beck signal generator. i use it for many different applications and havent found a version that i like. we are not talking apple-complexity. I would like an on/off+timer-program of say: 30min increments, and power output from 0-10, and a simple display that shows setting. How small do you possibly see this with the booster, battery, display with SMT-build? Would you like to help me out?

 

This LM358BP is aprox 1.45mm X 1.45mm X 0.7mm
Can this be used?

http://www.jameco.com/Jameco/Products/ProdDS/246588-DS27.pdf

 

Power output from 0-10 - the Beck circuit has a constant voltage fed through a variable resistor. Do you want to keep that, or have a fixed resistance fed by a variable voltage? The current through the load is the same either way (except in the millisecond near the transitions), but the output impedance will be significantly different.

ak

 

Power output from 0-10 - the Beck circuit has a constant voltage fed through a variable resistor. Do you want to keep that, or have a fixed resistance fed by a variable voltage? The current through the load is the same either way (except in the millisecond near the transitions), but the output impedance will be significantly different.

ak

Keep the voltage(or both). see the pic of the old PCB. Im not sure of the implications on the different impedance for the applications i intend to use it.

 

the applications i intend to use it.

? ? ?

 

I use

? ? ?

it for many different purposes, not only blood electrifcation. For powering a relay it could be useful to have variable voltage. Where can i find someone willing to help me redesign a smaller unit?