The right parts to make my project smaller....

So I have been working on a project for a few weeks now and am nearing completion. It is almost like a shield, giving added capability to a current product but my device is times the size of what is plugging into it. I have decided it is time to venture into SMD components but have never even tried to use them before. Now the resistors and capacitors and such are easy but I am using 2 TIP120 Darlington Transistors and I am certain they are overkill to begin with. each one is taking a digital pin held high (at 5v) and dumping it to ground when "told to". Any suggestions on a different component I can use would be great.

Also at current I am using an ATMega328P but only using 4 pins, I am considering using an ATTiny85 in its place. If anyone can point me to a good resource on how to set one up on a board that would be great, I have been looking but there are some that say all you need is power and others that show a whole slew of parts.

twelch: I am using 2 TIP120 Darlington Transistors and I am certain they are overkill to begin with. each one is taking a digital pin held high (at 5v) and dumping it to ground when "told to". Any suggestions on a different component I can use would be great.

As always, the rule is: "Post your code!"

In this case, post the circuit, specify what the parts are and explain properly what you need this part of the circuit to do. If you do no provide all the details, no-one can help you. "dumping it to ground when told to" means essentially nothing. :astonished:

Paul, I am a novice at best, I try not to use to many technical terms because I don't really know the vocabulary and I would prefer not to get blasted for using them wrong. I know a Darlington Transistor has a Base, a Collector, and an Emitter. When ever I think I know the correct definition of these terms, It turns out I have it backwards, or sideways or upside down or even worse I find a datasheet that uses different names for the pins. I can hook them up right by following the pictures and descriptions on data sheets but that's all I've got.

I chose to use "plain english" descriptions to keep things simple ( K.I.S.S. ). I have found that providing all the information about a project leads to replies and responses that are over detailed and reach into parts of the project that I don't want help with. Not because I don't think I need help but because I want to figure it out on my own. I feel its important to blow something up once in a while, bec ause then besides knowing what does work I also know what doesn't.

I personally feel that my description of what the Transistor is doing is pretty clear, one pin is the button and the other to are either side of an open switch, when the button is pressed the switch is closed, I shared that one one side of my switch I have 5VDC and the other is connected to ground. Pulling certain pins low by connecting them to ground generates certain responses from the original device the exact explanation of what they do is irrelevant to the question at hand.

Quite frankly the question is simple, What if anything would be a suitable smaller substitute for a TIP120 Darlington Transistor when only using 5VDC?

I understand that amps play a role to but I also said that I am using and ATMega328P which to the best of my knowledges keeps the amp limited to an extremely low number.

I also understand that for all the typing I just did I could have easily modified my post to be the way you want it but I felt it better if you understood why I posted it the way I did.

Now while we are picking apart peoples posts....

As always, the rule is: "Post your code!"

Code is irrelevent to this question

In this case, post the circuit

I am building a new circuit that will fit whatever parts I end up with. The old one is to big but as I stated above I don't want to be told how, I'd like to try to figure it out myself first. I am just looking for some options for parts.

specify what the parts are

I am using 2 TIP120 Darlington Transistors

and explain properly what you need this part of the circuit to do

each one is taking a digital pin held high (at 5v) and dumping it to ground when "told to".

Again, this is a simple "plain english" explanation because as stated above I don't know the technical explanation and if I messed that up you'd be blasting me for that instead.

So as you can see I was able to answer all your comments from details within the original post. So, Paul you could simply be nice and say " I'd like to help but I am not grasping what your question is" or something like that instead of tearing my post apart and claiming that nobody can grasp what I am asking.

twelch: Quite frankly the question is simple, What if anything would be a suitable smaller substitute for a TIP120 Darlington Transistor when only using 5VDC?

No it isn't. "5VDC" could mean many different things.

twelch: I understand that amps play a role

Yep.

twelch: I also said that I am using and ATMega328P which to the best of my knowledges keeps the amp limited to an extremely low number.

You're shorting a Mega328P pin to ground with a transistor? Is the pin set to output? If so, stop doing that.

Okay well whatever I'm done, It works the way I have it, it has been working for the last month so i;m not going to change it. The pins are set to input_pullup, i may be a newbie but i'm not completely clueless.

I reached out to an old high school buddy who I haven't talked to in years, gave him the same explanation I posted here and he rattled off half a dozen parts I could check out on mouser.com.

I think I will steer clear of the Arduino.cc forums for a while, It seems that one can't even be general in general section. To many people on here are more interested in there own ego's then the topics at hand. To many people think that every question need super-complexities in order to be valid and will make it a point to show off what they know and point out what you don't instead of answering a question.

Persecution complex much? Everyone's just trying to help. The problem with your "plain English" explanation is that it is ambiguous, and doesn't have all the information necessary to make a proper determination.

I reached out to an old high school buddy who I haven't talked to in years, gave him the same explanation I posted here and he rattled off half a dozen parts I could check out on mouser.com.

Just because he gave you part numbers, doesn't mean they are appropriate for the job at hand.

i may be a newbie but i'm not completely clueless

We don't know that unless you provide full details of what's connected to what and how they're set up.

So far we have discovered that the collector of your transistor is connected to a INPUT_PULLUP pin, and the emitter is presumably GND. What is the base connected to, a switch?

twelch: I reached out to an old high school buddy who I haven't talked to in years, gave him the same explanation I posted here and he rattled off half a dozen parts I could check out on mouser.com.

What parts did he recommend?

I have been using BSS84 as a general-purpose device for low power switching.

twelch: Okay well whatever I'm done, It works the way I have it, it has been working for the last month so i;m not going to change it. The pins are set to input_pullup, i may be a newbie but i'm not completely clueless.

I reached out to an old high school buddy who I haven't talked to in years, gave him the same explanation I posted here and he rattled off half a dozen parts I could check out on mouser.com.

I think I will steer clear of the Arduino.cc forums for a while, It seems that one can't even be general in general section. To many people on here are more interested in there own ego's then the topics at hand. To many people think that every question need super-complexities in order to be valid and will make it a point to show off what they know and point out what you don't instead of answering a question.

Yes, you should go with the first person that gives you an answer based on incomplete information. Don't bother with the people who actually try to help by first asking for clarification.

I'm not going to argue or debate with any of you. This particular section of the forum is labeled as a general area, I was looking for non-specific answers so I assumed this would be the right place. All I was asking is if there is a different item that does what a TIP120 Darlington Transistor does. I was not looking for advice on how to use or anything of that nature. Simple question - Simple answer.

Of the part numbers i was given only one turned out to fit my project. I had to look into them but thats all I wanted was a point in the right direction. I see people on here all the time that will flat out ask for someone to give them the answer. And these people get chewed out for not trying to figure it out on there own. Well I wanted to figure it out on my own and simply asked for a direction to look in. I am perfectly okay with popping a few chips here and there.

I don't understand why I can't ask a simple, generic, general question about a part without giving up my entire project. the details I did get into in my original post were only given to be conversational but whatever. I figured it out.

If your just looking for simple part substitutions at a lower spec you would be better off just telling the mouser search engine. It won't give you any attitude or hassle when you can't give it enough information to make a informed decision. ^_^

Unless you have the ability to design and make/order PCB's, going to SMT is un-necessary.

twelch: I don't understand why I can't ask a simple, generic, general question about a part without giving up my entire project. the details I did get into in my original post were only given to be conversational but whatever. I figured it out.

Of course, to the person asking the question it always seems easy and obvious. "Just tell me the part number I need to use!".

If you were to read your post without the knowledge you have, you would see a specific question was asked, which is impossible to answer without more detail.

In general, these forums are some of the friendliest and most helpful I've seen. "Newbies" don't usually get ragged on for ego reasons, it is invariably because more detail is required to give a sensible answer to the question.

I hope your friend gave you good advice. But forums work best as a two way thing, help others and they will help you.

twelch: I'm not going to argue or debate with any of you. This particular section of the forum is labeled as a general area, I was looking for non-specific answers so I assumed this would be the right place. All I was asking is if there is a different item that does what a TIP120 Darlington Transistor does. I was not looking for advice on how to use or anything of that nature. Simple question - Simple answer.

Of the part numbers i was given only one turned out to fit my project. I had to look into them but thats all I wanted was a point in the right direction. I see people on here all the time that will flat out ask for someone to give them the answer. And these people get chewed out for not trying to figure it out on there own. Well I wanted to figure it out on my own and simply asked for a direction to look in. I am perfectly okay with popping a few chips here and there.

I don't understand why I can't ask a simple, generic, general question about a part without giving up my entire project. the details I did get into in my original post were only given to be conversational but whatever. I figured it out.

I understand your stance..

but truly, (even if it comes off a bit abrasive).. over the internet, people are just trying to get a grasp of your skill level and try to get all people to understand & use the same terminology. (Its helps to keep people on the same playing field)..

but on the flip side... some of the people are here ALL THE TIME (by choice, un-paid, free-will they offer help)... and from time to time it can be frustrating when either the same questions are asked over & over.. or certain basic assets are omitted when seeking help. (help them help us sorta stance I guess)

Its also an attempt to understand the project fully, so they can provide a solid and correct answer. Sometimes that little missing detail can change the answer or optimal part of choice.

On the flip side.. many people are TRAINED professional and either are or have been doing this for many years. (so its easy for them to take certain things/knowledge for granted... or expect everyone to have the same foundation to work from)...

It can be frustrating to provide answers to 'hobbyists' at times....(I'm sure)... and at that point those members just need to either pass or ignore the post instead of being 'snarky'... IMHO though,.. I havent see any of that here, in this thread.

It seems that you are more frustrated with the lack of experience, making the questions/answers that much harder to interpret.

There are TONS of 'noobies' here (myself included, and you'll never make everyone happy, some only want the code in question, some want it all to put it into perspective...etc..etc.. yadda... yadda).. but I have found that if you can show you have gave an attempt, proof of effort, (links, datasheets, tutorials you worked from..etc) the response if much better. (it also makes it easier for them to help)

Good luck!

twelch:
I am using 2 TIP120 Darlington Transistors and I am certain they are overkill to begin with. each one is taking a digital pin held high (at 5v) and dumping it to ground when “told to”. Any suggestions on a different component I can use would be great.

TIP120 is large because its designed to dissipate a lot of power as heat. In order to
know what sort of SMT component can replace it you have to say how much voltage
and current are involved, ie some numbers, but you’ve gave no numbers at first.

Quite frankly the question is simple, What if anything would be a suitable smaller substitute for a TIP120 Darlington Transistor when only using 5VDC?

Still need to know the current.

I understand that amps play a role to but I also said that I am using and ATMega328P which to the best of my knowledges keeps the amp limited to an extremely low number.

power = volts x amps, when a darlington is on there is perhaps 1.5V, so the power is
1.5 x current in amps.

The gain of a darlington is in the 1000 to 10000 range, so the ATMega328P, which can
output 40mA can’t really limit the current since 1mA is enough to totally saturate the device.

Its really important to read the sticky thread about how to post here so we don’t have to
keep repeating what it says piecemeal.

Code - post it…
Circuit - post it…

Or at the very least explain what sort of load you are switching - how much current,
what is it (inductive loads behave completely differently for instance - we need to
know if its an inductive load).

I understand that amps play a role to but I also said that I am using and ATMega328P which to the best of my knowledges keeps the amp limited to an extremely low number.

Exactly. To the best of your knowledge, which from what you have said here is incomplete.

The Arduino does not limit current. The voltage and load limit current. Unless your load would draw more current than the regulator can handle, then the voltage will drop from overload.

"... amps play a role..." Yes, that is a very important number. Perhaps your load is only drawing 20mA, and you are using a TIP120 merely because it is what you had on hand, or because you didn't understand that they are overkill for your purpose. You have indicated that you don't know how to select a transistor, after all. Or perhaps you are running at the limit of what that transistor can handle. Those two situations would necessitate entirely different answers.

We are actually trying to help you. You are a free agent, do what you wish.

I completely believe that some may be trying to help, but other are just puffing thier own ego's. It keeps being repeated "post your code" "post your schematic" but I already stated --THEY DON'T EXIST YET!!!

Now I admit my short comings and admit that I am a rookie and perhaps my question was stated wrong, and when i tried to restate my question my own anger led to further confusion, I will try to restate when I am done with this rant. This section of the forum is labeled GENERAL. Meaning non-specific. I can take blame for giving to many unneccisary details and can see how that would lead people to believe the project is further along then it actually is BUT this is not the first time I have tried to ask a generic question and been blasted by others who while they have themselves convinced they are trying to help they are really only trying to boost thier own ego's by saying "look how smart I am". This is not directed at anyone, because quite frankly it is really impossible to tell who falls into what category in this arena. If you take offense from my statement then it is only yourself questioning your true motives.

OK, so simple descrition of the situation....

I have a device, the device has a pin that is held high at +5VCD, my multimeter gives no reading for amps(no load no amps right?). When this pin is "pulled low" certain functions of the device shut off(allowing its battery to last longer). I want to use my arduino to control when this happens but don't know what part to use. I was able to accomlpish this using what I thought was TIP120 NPN Darlington Transistor, turns out someone moved the drawers around and it was actually a TIP120 NPN MOSFET Transistor, I tried using it because only because I happened to have a few but it is overkill in both ratings and size. While investigating a few part that were recommended to me I found that a transistor may be wrong altogether, and there are a multitude of device that could accomplish this task. I have found with some of them the fact that there is no actual load can cause problematic operation. I am NOT asking HOW to do this, I really want to figure it out on my own but I do need recomendations for components I can look at as possible solutions. think generic, a device to connect the 5VDC to ground when signaled.

Okay well whatever I'm done, It works the way I have it, it has been working for the last month so i;m not going to change it.

It keeps being repeated "post your code" "post your schematic" but I already stated --THEY DON'T EXIST YET!!!

I won't bother you any more.