Looking for a dual line driver to run some LEDs and interface with some other circuits. Found this on Newark: 'SN75121N' [Line Driver, Dual, TTL, 4.75V to 5.25V Supply, DIP-16] But I don't like that its TTL and probably a current hog.
Need the drive to run at 3-6v Thank you.
What exactly are you trying to do? You might look at prebiased transistors for the LED driving job, or for a through-hole approach,
2N7000s with one resistor each.Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
What LEDs are you driving? What are the LEDs doing or indicating? A schematic would help.
I've seen many mistakes with something as simple as driving an LED. There's thinking that some expensive driver chip has to be used. There's thinking that an open collector/drain output has to be used. There's thinking that a pullup resistor is needed in addiditon to the LED series resistor. A single transistor and one or two resistors can drive an LED and depending on where you put your resistor it can keep the LED current reasonably constant over a wide suppy range.
If we don't know exactly what you're trying to achieve then this thread could easily get longer than the 741 thread.
I am just trying to drive a couple of LEDs and also supply that output to another logic board and/or relay. Looking at the specs from the chips that have a max output current of < 10mA, I thought that using a simple chip to drive the LEDs and relays would be simple, but if its not then I need that answer as well. Thank You.
Edward Rawde wrote: ==================
** Characters like " sidw...." posting via gmail.com are never going to tell you that. Cos then you would know their "secret" and likely not help any more.Mostly their project is either crazy, illegal or dangerous - sometimes all three.
IMO: if you do not know what the poster is up to, DO NOT HELP !!
BTW: Q. Why is "gmail " so bad ?
A. Because several years ago "Google Groups" began and opened the flood gate to every stinking troll on the internet to access usenet.
Ever since, usenet has fallen into decline and disrespect. Hardly anything left now.
....... Phil
Most LEDs these days are blinding at a mA or two. We run maybe 100 uA for test led's on pcb's, so we can see around them to probe. Most LEDs are visible in office light at 1 uA.
I tested one green LED up at the cabin on a moonless night, dark adapted at 2AM, and I could just make out light at about 1 nA.
Are we allowed to see those specs? I found the spec of the 75121N like this:
My answer, without knowing more, is one transistor and one resistor for each LED. The resistor goes in the transistor's emitter circuit.
A hex inverter sounds like the ticket. 74HC04 or its brethren.
For a DIP package see e.g.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
I may have found a possibility, TI has a chip 'SN75451BP', The NAND gate version. Specs:
I thought about using a inverter or even just a quad AND gate, but if I can find a chip that was designed and intended for this function would be a better option.
{snip}>> I may have found a possibility, TI has a chip 'SN75451BP', The NAND gate version.
I'm curious why you think that a "chip that was designed and intended for this function would be a better option" for driving an LED.
Does moving a fridge require an individual that was designed and intended for this function or can anyone do it?
That's the germ of a TERRIBLE plan. Every chip manufacturer has a sales force that wants to convince you that your intention fits their chip. But the intention that matters is YOURS, the designer's, not the chip manufacturer's.
On Wednesday, January 20, 2021 at 3:03:48 PM UTC-5, snipped-for-privacy@gmail.com wrote :
ther circuits. Found this on Newark: 'SN75121N' [Line Driver, Dual, TTL, 4.
75V to 5.25V Supply, DIP-16] But I don't like that its TTL and probably a c urrent hog.If 5.5V operation is good enough how about this?
The AC product line gives the current you are asking for. If you are tryi ng to drive a line without any specific specs on timing, what's wrong with a simple transistor. Use the LED as your pullup/down with a current limite r resistor in series with the LED and a resistor in parallel with them to a ssure pull to the rail.
-- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
True, mostly these groups are full of whiny old men decrying the loss of their domain.
-- Rick C. + Get 1,000 miles of free Supercharging + Tesla referral code - https://ts.la/richard11209
Huh? If you thought the 75451 was power hungry....
ICCL Supply current, outputs low VCC= MAX, VI= 0V SNx5451B52 65 mA
What's wrong with a FET like the 2N7002? Good up to 20V on the gate and more on the drain. 100's of mA. If you are driving a relay protect from kickback with a diode across the relay.
-- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
Congratulations on picking a 53-year-old part. There aren't that many of those around. ;) (At least it isn't super-expensive.)
Driving a few LEDs and shipping around 10-mA-level binary signals really doesn't require this level of drama, though. Why not pick something less current-hungry such as the above, or (if you need HV open-collector outputs) a prebiased (or 'digital') transistor array such as
?Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
logic gates are generally suitable for driving indicator LEDs describe the task in more detail. Quantify your requirements.
There are specialised LED driver chips, but seeing as you only have one or two LEDs they seem like probably overkill
-- Jasen.
Do they still make ULN-2000 series multiple darlington drivers ?
Probably an overkill for your application, unless you need high voltages or high currents yo drive your relays.
Yes, and super-cheap/available and wil be for a very long time. And flyback diodes built in for inductive loads.
However if you need to run an LED at 3.3V they have a bit too much drop.
Maybe a nickel in 1K for a cloned one.
Best regards, Spehro Pefhany
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