LED strobe circuit needs more current

[Harald Kapp]

No problem:
4.5V ... 18 V for the bipolar version.
1.5 V ... 12 V for the CMOS version (e.g. LMC555).

The CMOS versions requires less current. Otherwise it can be used in the same way as the bipolar version.

Harald

 

[CocaCola]

Thanks Harald.. I thought I read somewhere that the 555 may require more than 5volts to operate? Will this circuit work with only 5vdc?

Read the datasheet for the 555 you choose, almost all will work with 5V, it's bellow that that most will have issues...

*** Edit Harald cut me off at the finish line

 

[CDRIVE]

Thanks Harald.. I thought I read somewhere that the 555 may require more than 5volts to operate? Will this circuit work with only 5vdc?

The LM555 is (supply and output) TTL compatible. TTL is a 5V logic family. So, yes, it's 5V compatible. That said, batteries do drain. You'd be better off running it off >5V.

Chris

Edit: You all beat me to the finish line!

 

[trondyne]

The LM555 is (supply and output) TTL compatible. TTL is a 5V logic family. So, yes, it's 5V compatible. That said, batteries do drain. You'd be better off running it off >5V.

Chris

Edit: You all beat me to the finish line!

Hmm for this application the supply may well be below 5vdc even though a regulator may be present.. But when running off nimh packs the nominal is 4.8 I think. So then the voltage range should probably be ~4.5 to 6vdc if possible.

 

[CDRIVE]

Hmm for this application the supply may well be below 5vdc even though a regulator may be present.. But when running off nimh packs the nominal is 4.8 I think. So then the voltage range should probably be ~4.5 to 6vdc if possible.

There's more than a single model of the 555. Did you read Harald's post?

No problem:
4.5V ... 18 V for the bipolar version.
1.5 V ... 12 V for the CMOS version (e.g. LMC555).

The CMOS versions requires less current. Otherwise it can be used in the same way as the bipolar version.

Harald

Chris

 

[trondyne]

There's more than a single model of the 555. Did you read Harald's post?





Chris

Yes just restating the voltage req.

I have two 555s now is there a way to tell which type they are?

 

[CDRIVE]

If there's a "C" in the part number then it's CMOS. There is a trade off for the lower voltage operation though. You can't drive high current LEDs directly from the CMOS models. You will need a driver transistor. If your Darlingtons are power transistors they will work. A better choice would be a logic level FET though.

Chris

 

[trondyne]

Then with a cmos it would require an additional power relay so to speak... Then it would be using quite a few components including the 555 which contains something like 25 and the original circuit components..

Is this the best choice then? I would have thought this could be handled by a relatively small number of components even without the 555.

 

[CocaCola]

I would have thought this could be handled by a relatively small number of components even without the 555.

The 555 isn't that involved don't focus so much on part count... You can use a 556 if you need two 555s in a single chip... And you can use a Darlington IC chip like the ULN2003 that has all the transitors as well as base resistors all in one chip to reduce parts count significantly...

A micro would reduce overall part count significantly, but there is an upfront investment and learning curve to program them...

 

[CDRIVE]

The component count within a chip is rather irrelevant. The 555 has 8 pins. That's all you have to deal with. It wouldn't matter if there were 10,000 in there.

Chris

 

[trondyne]

The component count within a chip is rather irrelevant. The 555 has 8 pins. That's all you have to deal with. It wouldn't matter if there were 10,000 in there.

Chris

I didn't mean to count the internals, just counting the 555 as one component plus the rest + additional amp I think makes for a higher part count than the original circuit. I am just trying to keep it cheap and as simple as possible.

 

[CocaCola]

I think makes for a higher part count than the original circuit. I am just trying to keep it cheap and as simple as possible.

Did the original circuit suit your needs and do what you need? If the answer is no, then you have to kinda assume that adding those needs to the existing circuit will increase the complexity... As for cost we are talking a few dollars total here, you are penny pinching at the lose of functionality at this point...

 

[CDRIVE]

Then with a cmos it would require an additional power relay so to speak... Then it would be using quite a few components including the 555 which contains something like 25 and the original circuit components.. Is this the best choice then? I would have thought this could be handled by a relatively small number of components even without the 555.

I didn't mean to count the internals, just counting the 555 as one component plus the rest + additional amp I think makes for a higher part count than the original circuit. I am just trying to keep it cheap and as simple as possible.

Well I don't know what adds up to 25 +?.

I like to guess what people are building. Is this a bicycle flasher?

Chris

 

[trondyne]

Well I don't know what adds up to 25 +?.

I like to guess what people are building. Is this a bicycle flasher?

Chris

Is this really a big deal?

I thought I remembered the 555 contains something like 25 components.. Moreover it is my job to try to keep costs down--if possible--regardless of what folks think of me--low cost was listed in the req..

Nope not a bike thingy.

 

[Harald Kapp]

I didn't mean to count the internals, just counting the 555 as one component plus the rest + additional amp I think makes for a higher part count than the original circuit. I am just trying to keep it cheap and as simple as possible.

The original circuit contains 8 parts (without battery). The circuit I linked (555 based) also requires 8 parts. Part count is identical and therefore cannot be the sole criterion. Don't count parts, sum up the component's prices. I think that's what you should have asked in the first place.

If you want to go really minimalistic, have a look at this circuit or this circuit: only 5 parts including the LED. And both circuits use only very cheap components.

 

[trondyne]

The original circuit contains 8 parts (without battery). The circuit I linked (555 based) also requires 8 parts. Part count is identical and therefore cannot be the sole criterion. Don't count parts, sum up the component's prices. I think that's what you should have asked in the first place.

If you want to go really minimalistic, have a look at this circuit or this circuit: only 5 parts including the LED. And both circuits use only very cheap components.

I'm sure the price is okay, again just want to keep it lowish... I should have asked what in the first place?

I can't go with any custom design right off... I need something first as a stop gap measure hence the original circuit or else I will have to wait for the custom design to complete.

 

[CocaCola]

Is this really a big deal?

You can best answer that since you brought it up...

I thought I remembered the 555 contains something like 25 components..

As has been said, it only has 5 pins, why worry about what is inside?

Moreover it is my job to try to keep costs down--if possible--regardless of what folks think of me--low cost was listed in the req..

Does functionality of the devices come into play with the price?

A 555 (CMOS) timer can be had for about 45 cents...
A ULN2003 Darlington chip can be had for 35 cents...
A 10K pot for speed adjustment can be had for about 55 cents
A couple resistors and caps can be had for maybe $1 to round it off...

Total cost about $2.50 with full functionality as you described, what was your target price? And how much functionality are you willing to compromise to get to that price?

 

[(*steve*)]

it only has 5 pins

For very large values of 5.

 

[CocaCola]

For very large values of 5.

Got me there, but only 6 unique connections in this configuration

 

[trondyne]

You can best answer that since you brought it up...



As has been said, it only has 5 pins, why worry about what is inside?

Does functionality of the devices come into play with the price?

A 555 (CMOS) timer can be had for about 45 cents...
A ULN2003 Darlington chip can be had for 35 cents...
A 10K pot for speed adjustment can be had for about 55 cents
A couple resistors and caps can be had for maybe $1 to round it off...

Total cost about $2.50 with full functionality as you described, what was your target price? And how much functionality are you willing to compromise to get to that price?

Price is fine.