Converting cordless devices

[Demon]

http://www.kijiji.ca/v-power-tool/ci...r-13/551178168

Mine didn't come with a case. Replacement batteries cost about $2 each(2 batteries), but $32 shipping! Then add tax, duty and brokerage fees, it's just nuts - we live in a throwaway society.

But I love these and want to convert them to "non cordless", got 2 and they worked great. I was thinking of using a 5V wall adapter and 2 diodes inside the grip to lower the voltage to 2.4V.

I could use suggestions/comments. I have no clue how much current they used. The battery is 1100mAh, so it couldn't have been a lot.

Robert

[Demon]

Turns out the 4.5VDC 300mA wall adapter puts out 7.75, 7.85 and 7.95VDC (I found a 3 screwdriver).

The motor is a Leshi Motor 3805-30205, 3.6V, 030925/B.

This screwdriver has no controller circuit, , just a switch, 2 batteries and power jack. It runs with wall adapter connected with these old 7yr+ batteries.

Voltage at motor is 2.65V using wall adapter and 2 batteries still connected, gradually dropping. Does the same using the batteries only.

(still testing)

Robert

[Demon]

Note for the next guy:

The batteries offer more than cordless feature, they provide a ton of current. LOL

Plan B: run off a rechargeable battery on the workbench.

Robert


Edit: and don't ask me why I can reassemble a complete cordless screwdriver gearbox.

[Demon]

Current on this seemingly mild motor spikes at 4.5A on power-up, settles quickly at 1.5A during operation (without resistance).

A 12V 7Ah battery turns it plenty fast, worried to hurt gearing.

12V from a PC power supply turns it a bit slower but still too much. I wanted to use a 7808 but they seem to have a max of 1.5A, I need an 8V source than can handle a 5A spike.

(Googling for 8V NiCD batteries)

Robert


Edit: the LM338 can operate at 5A from 1.2-32V with a 7A peak. I'm kinda worried of running a 7808 at 1.5A for an extended period.

The other thing I can think of is a MOSFET controlled by PWM from a PIC.

[Demon]

Don't you hate searching for replacements, not finding any at a reasonable cost, so you move on to customizing and then this pops up.

10 x NiCd 4/5 SubC 1.2V 1600mAh
Rechargeable Battery with Tab Blue
$16.16USD

http://m.ebay.ca/itm/130807945134

So I could bring life back to all 3 screwdrivers for just over $17 Canadian.

Robert