I screwed up nicely

[Tony Stewart]

there may be a trivial solution, if you can define the situation exactly

 

[tvtech]

Three mistakes..

1. Op Amp has a conventional push/pull output that sources current
2. Comparator has an output that sinks current.
3. They don't play the same

Anyone wanna chime in?

AFAIK they are not replaceable devices as far as getting stuff to work.

I forgot. And it's going to cost me.

tv

 

[Tony Stewart]

Only 1 mistake.
No specs, including logic diagram.
load current, voltage ='?
Can easily be fixed. No drama.

 

[KeepItSimpleStupid]

This https://www.maximintegrated.com/en/products/analog/amplifiers/MAX931.html one sources 40 mA.

So, maybe she's wearing one for her lover.

 

[tvtech]

Anyway, me proud of doing previous boards properly

This one is good @ it's main function....namely charging little PP3's.
It can do that for ever with 2 separate channels charging.

8.4V blocks never overcharge. 10V MAX is where all stops. Forever.

Monitoring is the killer. Turning an LED on or off when 10v is approached..

Just to give a visual indication. That's all.

Charger excellent....Monitoring a PITA.....almost there now.

Sure I can buy chips that do that and Supervise......and no profit.

So, once again I am getting there. Bits and pieces and making space on a tiny board

And sweating and smiling.....I'm almost there

I keep forgetting its a BATTERY CHARGER.......not a LAB PSU....

Things, things, things.

My mind overheating now.

And so on,
tv

 

[fezder]

From my understanding, opamp can be used as comparator for some degree, but not other way around (comparator cannot do amplification stuff) and comparators are mostly faster & can handle more current....Good to know I'm not the only one who stumbled on this issue

 

[tvtech]

So good to see you again Fez

Whew. Me feeling kinda retarded

 

[alec_t]

comparator cannot do amplification stuff

Actually it can, albeit with some limitations, if it has a pull-up resistor on the output. Distortion and stability may well be different from those of a dedicated opamp.

 

[fezder]

Well, that's new, thanks alec! But how, since comparator output is eihter 1/0?

 

[tvtech]

What makes things more difficult is you get Comparators that use Class AB output too...
Not only Open Collector...

Either way I screwed up.

You must see what my prototypes look now....

Never mind.

Me go sleep. Me fix all and not make same mistake again

tj

 

[fezder]

tj

almost dj ;D

 

[alec_t]

But how, since comparator output is eihter 1/0?

That's how it's normally used, but the output of an open-collector type (e.g. LM339) with a pull-up resistor and negative feedback can be made to take up an intermediate position. It is, after all, a very high gain differential amplifier.

 

[fezder]

Why oh why electronics can't be simple? Thanks alec

 

[audioguru]

You cannot use negative feedback with a comparator since it does not have "frequency compensation" like used in an opamp.

How does your PP3 charger know if the "9V" battery has 6 cells or 7 cells?
You selected 8.4V as "blocks never overcharge" but if the battery has 6 cells then each cell is 1.4V and might be fully charged but if the battery has 7 cells then it is no where near fully charged.

A PP3 battery such a high internal resistance so if it is charged at a fairly high current for "fast charging" then each cell reaches 1.4V long before they are fully charged.

 

[tvtech]

You cannot use negative feedback with a comparator since it does not have "frequency compensation" like used in an opamp.

How does your PP3 charger know if the "9V" battery has 6 cells or 7 cells?
You selected 8.4V as "blocks never overcharge" but if the battery has 6 cells then each cell is 1.4V and might be fully charged but if the battery has 7 cells then it is no where near fully charged.

A PP3 battery such a high internal resistance so if it is charged at a fairly high current for "fast charging" then each cell reaches 1.4V long before they are fully charged.

Hi AG

Most modern PP3 are 8.4 blocks. Seven cells.
Ansmann recommend MAX charge @ 10.15V.

I have three cheap(not really) Camelion Chinese 8.4 blocks that have loved the way I charge them.

Easily got around 500 to 700 cycles. No sweat.

Been charging and discharging for three years now. Never a failure. They just "wear out" or gradually loose Capacity.

Proper PP3 chargers are hard to find.

That is why there are very few on the Market worldwide
A little PP3 is like a cold Woman....sort of.

Umm..like....Don't excite me or make HOT?
Just charge me normally and quickly and look after me...
When I am at Terminal Voltage.....keep me there forever.
Then I can look after you forever too

Sigh

I'm in love with a sexy, charged PP3. PP3 is the one. PP3 might not have an hourglass figure.....she never gets HOT, just there for me.

So, there, is the confirmation that I have officially gone mad.

Somebody shoot me please

tv

 

[tvtech]

Before I get shot, I am going to try a 741. Last try. Flipping expensive now though..

Could just solve my problem. They are not so darn sensitive

I know "stuff" as far as CRT goes. This thing though has me stuffed. For the life of me I dunno why this simple "indicator" will not work properly..
Why

Pulling my hair out.

1. Got stable 431 ref voltage
2. Two channels. Two separate everything....
3. The one channel affects the other????
4.PSU stable
5. Why????

O mother of God have mercy on me.

I thought I knew stuff. I proved myself wrong.
I know squat

I'm outta ideas and crawling like a retarded insect begging for help.

Don't shoot me. Just spray me. Any insecticide will do.

tv

 

[ronsimpson]

I am going to try a 741

Make certain that the AudioGuru bless it first!

 

[tvtech]

Seriously I don't know how to fix this. Nothing makes sense Ron

 

[tvtech]

I read somewhere on the NET that dual op amps sometimes are not really independent...like can influence each other?

Not in this case. I am just having bucket loads of crap with this

Why?

 

[ronsimpson]

Nothing makes sense

I went back 10 posts. Where is your schematic?