View Full Version : ARP : 7812 and LM 317 ???

12-16-2004, 06:53 PM
Hi all

I was building a basic cicuit and here are a few question :)

Should i put in a battery charger ... simple lm 317 based ( Ni -cd and Mh ) ??? what do you say

Also do you think putting in 7812 will be a good idea ( for motors ) ??? Or a simple 7805 is enough

12-17-2004, 10:42 AM
Just clip in a 7805 for all control logic..

The motors can be run externally...most of the time they do not need regulators...

12-17-2004, 10:47 AM
Just a suggestion..
wont it be good to have a regulator or supply unit..just like an SMPS..delivering voltages like 5V,6V,9V,12V..

They can be routed to required boards from there

12-17-2004, 01:14 PM
I think its a smart idea to put in a charger.... 317 or equivalent... have the batteries been decided ?

With NiMH rechargeables.. its this ever going to fit into 1k ??

It is'nt a good idea to add a 7812 for the motors though... linear regulators have huge Vce*I losses.... a Switching supply (or PWM) is better... although i dont get why a direct connection wont do... Is there feedback planned - i.e. is the motor circuit a closed loop?

12-17-2004, 03:23 PM
ill drop 7812 but keep lm 317 .

Ni cd - 8 battries cost abt rs 160 [ 800 mha ]

Ni - MH - dunt know the price

anyay if you intend to use the charger can charge both .

12-19-2004, 08:49 PM
I bought 8 Samsung NiMH 2100mAH batteries a few days ago....cost me a whooping 900 Bucks + charger another 200 bucks. But i would say the performance was worth it.

One thing I would like to point is that NiCd would get heated up if more than two toy dc motors are run...it boils down to a tradeoff between performance & cost.....

12-19-2004, 08:54 PM
NiMH take arround 10 hrs to charge on 200mA standard charger ..... it's the other drawback