CA3140 & LM3140 op-amps?

[Bazz4CQJ]

Originally Posted by G.Castle

Article referred to in post 11

http://www.americanradiohistory.com/...search=%22mini motor power booster%22

Thanks for that; I'll take a close look at it. I'll need to be more awake than I am this minute to figure out how to change it to work with a 12V drill.

How I wish it were July 1972 again, and that I knew then what I know now .

B

[RichardGM]

I'm bemused by the references to constant torque, when the circuit linked from post #1 is designed to maintain constant motor speed when the load, and therefore the required torque, change.

[Bazz4CQJ]

Originally Posted by RichardGM

I'm bemused by the references to constant torque, when the circuit linked from post #1 is designed to maintain constant motor speed when the load, and therefore the required torque, change.

Well, at this time when there is not too much to be happy about in the World, I'm very please to have provided you with some distraction .

For anyone who is interested, I'm currently building a second controller with the 535 and LM1084, as my first one worked very well...until I reversed over it. I may have a look at the old PE design later, but the workshop is busy building new boards for my 163 at the moment....mmmm the smell of Dalo pens and ferric chloride do so take me back.

The concerns about the CA3140 have been noted!

B

[David G4EBT]

Back in 2015 I made a homebrew Pulse Width Modulated drill speed controller for drilling PCBs.

It's done a lot of work since then and still works a treat.

I wrote it up as a forum thread, the link to which is here if it's of any interest.

"A Homebrew 12V PCB Drill Speed Controller":

https://www.vintage-radio.net/forum/...d.php?t=118653

I claim no credit for the circuit, which I found on internet and don't have the link to it. I just designed the PCB for it, but I guess it could be built on strip-board if need be, though I guess that anyone who is likely to be homebrewing PCBs (if anyone does any more, now that Kicad and JLPCB can do that at a fraction of the cost), would want to build it on a PCB.

The explanatory notes with the circuit stated:

Quote:

PWM (Pulse Width Modulation) is an efficient way to vary the speed and power of electric DC motors. The described circuit can be used to vary the speed of small electric PCB drill. The circuits can quite easily be built on a standard prototyping board. The power component (IRL510N) must be connected to the power rails and the drill motor with quite thick wires and cables.

As used here, a Power MOSFET motor driver is better than the traditional driver because it is working at a higher switch frequency, and this also avoids the unnecessary voltage drop and power loss.

Electrically a DC motor can be viewed as a series RL network with a voltage generator. The generator represents the back electromotive force (BEMF) generated by the motor’s rotation and which opposes the electromotive force of the supply. Diode D3 (1N4007) is added to protect the electronics from BEMF. Diode “MBR 1645” is a better alternative

STP22NE10L (100V/<0.085R/22A) can be used in lieu IRL510N (100V/0.10R/17A).

End quote.

I used an IRL530N, which is still cheaply and readily available:

http://www.ebay.ie/itm/IRL530-N-chan...-/201048729480

Hope that's of interest.

[Bazz4CQJ]

Thanks for that suggestion Dave; I've owned a PW controller for a long time, and that's what I've been using this week and it's done what I needed (drilling 3 fibreglass PCB's at a time). The "load sensing" controller was better I think, and that's why I'm building another one. As mentioned previously, that's a LM353 driving a LM1084.

B