Powering Pic16F84A - Page 2 - Electronic Circuits Projects Diagrams Free

ericgibbs · 27th September 2007, 03:53 PM

hi paparts,
My first reaction is that circuit will not give reliable operation with 6Volt Bty pack of ZiC batteries, especially with the diode in series with the battery.

The motors must pull down the battery voltage below the safe working voltage of the PIC, also the 555 is driving an 8

hm: speaker, that must be trying to draw a heavy pulse. [the spkr needs a series resistor]

You need a more heavy duty battery pack with a voltage regulator.

Thats why the project works OK on a bench power supply.

blueroomelectronics · 27th September 2007, 11:31 PM

It's similar to my Mongoose robot kit. I'm using 4xAA NiMH 2300MAh batteries and 470uf caps on both the H-Bridge (I use a CD754410) and it works fine.

paparts · 28th September 2007, 07:36 AM

So what can u suggest?

ericgibbs · 28th September 2007, 07:59 AM

Quote:

Originally Posted by blueroomelectronics

It's similar to my Mongoose robot kit. I'm using 4xAA NiMH 2300MAh batteries and 470uf caps on both the H-Bridge (I use a CD754410) and it works fine.

hi Bill,

The OP says he is using Zinc Carbon batteries, which have a low specification.

Paparts..
Why not try the battery type/rating that Bill uses, it should be fairly easy to substitute NiMH for Zinc batteries.
Also add the bridge capacitors.

paparts · 28th September 2007, 12:12 PM

Can I ask for the diagram? I could not find the specs of CD754410

ericgibbs · 28th September 2007, 12:24 PM

Quote:

Originally Posted by paparts

Can I ask for the diagram? I could not find the specs of CD754410

hi,
I cant find the CD754410 data ?

Have you tried a NiMH battery pack??

paparts · 28th September 2007, 03:55 PM

Have'nt yet maybe tomorrow coz its night time here. Ill give you an updtae on how I will solve it if ever. I have an idea using LM7805 a voltage regulator. My friend used a voltage regulator and it went well.

ericgibbs · 28th September 2007, 03:59 PM

Quote:

Originally Posted by paparts

Have'nt yet maybe tomorrow coz its night time here. Ill give you an updtae on how I will solve it if ever. I have an idea using LM7805 a voltage regulator. My friend used a voltage regulator and it went well.

You cant use a 7805 with a 6 Volt battery pack.

mvs sarma · 28th September 2007, 05:51 PM

1. How far it would be proper to drive BD436/436 transistors from thr port pins of PIC16F884 without even base current limiting resistors?

2. Whether the PIC cant be tried at 4.5V which is amounts to use three cells

3. After somuch extensive circuitry and anticipated load current , perhaps it would be appropriate to use a 6V lead acid battery of 2 or 3AH capacity and try using LDO regulator for supplying the PIC.

**Nigel Goodwin** · 28th September 2007, 05:54 PM

Quote:

Originally Posted by mvs sarma

1. How far it would be proper to drive BD436/436 transistors from thr port pins of PIC16F884 without even base current limiting resistors?

Don't do it!.

Quote:

2. Whether the PIC cant be tried at 4.5V which is amounts to use three cells

Works fine, it's common practice.

Quote:

3. After somuch extensive circuitry and anticipated load current , perhaps it would be appropriate to use a 6V lead acid battery of 2 or 3AH capacity and try using LDO regulator for supplying the PIC.

Easiest method is to use 6V for the motors, and 5V regulated from a seperate 9V battery for the electronics - this cures LOT'S of potential problems.

mvs sarma · 28th September 2007, 08:36 PM

Hi, Nigel,
I was aiming these comments on the schematic posted by Paparts on 27th instant.

blueroomelectronics · 28th September 2007, 11:08 PM

google cd754410 or l293d same pinout. The l293 might be easier to find, it'll work with small dc motors up to 600ma (the cd745510 will handle 1.2a)
Carbon Zinc batteries have a much different discharge curve than NiMH. Plus NiMH AA are about 1.2v per cell so four will give you 4.8v fully charged.

mvs sarma · 29th September 2007, 06:15 AM

Quote:

Originally Posted by blueroomelectronics

google cd754410 or l293d same pinout. The l293 might be easier to find, it'll work with small dc motors up to 600ma (the cd745510 will handle 1.2a)
Carbon Zinc batteries have a much different discharge curve than NiMH. Plus NiMH AA are about 1.2v per cell so four will give you 4.8v fully charged.

All said, for a robot project, it is preferabale to go for high capacity and light weight batteries as these have to be carried on the body of the robot. As such perhaps two li-ion celles in series may be better provided re-charging system could be managed.

blueroomelectronics · 29th September 2007, 06:57 AM

Li-Ion cells are somewhat expensive and require an exotic charger to keep from exploding. They hate being abused and a short might anger them (see explode, fire etc...)
NiMH are common and more forgiving.

PS the OP seems to be having a difficult time giving up on the Carbon Zinc cells.

mvs sarma · 29th September 2007, 06:02 PM

Quote:

Originally Posted by blueroomelectronics

Li-Ion cells are somewhat expensive and require an exotic charger to keep from exploding. They hate being abused and a short might anger them (see explode, fire etc...)
NiMH are common and more forgiving.

PS the OP seems to be having a difficult time giving up on the Carbon Zinc cells.

There are fresh cells named 'ZIC CHLORIDE CELLS" and these give better discharge rates. they are generally used for photography at nominal cost -- unlike Duracells.

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27th September 2007, 03:53 PM	(permalink)
ericgibbs	hi paparts, My first reaction is that circuit will not give reliable operation with 6Volt Bty pack of ZiC batteries, especially with the diode in series with the battery. The motors must pull down the battery voltage below the safe working voltage of the PIC, also the 555 is driving an 8hm: speaker, that must be trying to draw a heavy pulse. [the spkr needs a series resistor] You need a more heavy duty battery pack with a voltage regulator. Thats why the project works OK on a bench power supply. __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/ Last edited by ericgibbs; 27th September 2007 at 03:56 PM.

27th September 2007, 11:31 PM	(permalink)
blueroomelectronics	It's similar to my Mongoose robot kit. I'm using 4xAA NiMH 2300MAh batteries and 470uf caps on both the H-Bridge (I use a CD754410) and it works fine. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

28th September 2007, 07:36 AM	(permalink)
paparts	re: So what can u suggest?

28th September 2007, 12:12 PM	(permalink)
paparts	Re: Can I ask for the diagram? I could not find the specs of CD754410

28th September 2007, 03:55 PM	(permalink)
paparts	Re: Have'nt yet maybe tomorrow coz its night time here. Ill give you an updtae on how I will solve it if ever. I have an idea using LM7805 a voltage regulator. My friend used a voltage regulator and it went well.

28th September 2007, 05:51 PM	(permalink)
mvs sarma	1. How far it would be proper to drive BD436/436 transistors from thr port pins of PIC16F884 without even base current limiting resistors? 2. Whether the PIC cant be tried at 4.5V which is amounts to use three cells 3. After somuch extensive circuitry and anticipated load current , perhaps it would be appropriate to use a 6V lead acid battery of 2 or 3AH capacity and try using LDO regulator for supplying the PIC. __________________ Regards, Sarma.

28th September 2007, 08:36 PM	(permalink)
mvs sarma	Hi, Nigel, I was aiming these comments on the schematic posted by Paparts on 27th instant. __________________ Regards, Sarma.

28th September 2007, 11:08 PM	(permalink)
blueroomelectronics	google cd754410 or l293d same pinout. The l293 might be easier to find, it'll work with small dc motors up to 600ma (the cd745510 will handle 1.2a) Carbon Zinc batteries have a much different discharge curve than NiMH. Plus NiMH AA are about 1.2v per cell so four will give you 4.8v fully charged. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

29th September 2007, 06:57 AM	(permalink)
blueroomelectronics	Li-Ion cells are somewhat expensive and require an exotic charger to keep from exploding. They hate being abused and a short might anger them (see explode, fire etc...) NiMH are common and more forgiving. PS the OP seems to be having a difficult time giving up on the Carbon Zinc cells. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com