Starting hardware

[Dreeass]

I recently ordered my first Pi and I'm getting ready to order the hardware for it like wires, but I'm not very experienced and would like some advice about the stuff I'm going to buy. This is my note on Evernote that has some links to a store which is Dutch, but you'll most probably be able to read the specs and if not you can use Google translator.

Also I haven't managed to find resistors, I'm used to Ohm but when I check the website I see stuff about Watt and don't know what to pick. I need resistors to be able to use the LED's and some information. The last thing is for someone to explain me how headers work, female and male headers, do you put them on or do you have to melt them together?

I know that it is a lot to ask, but I'm really into this since I started programming a while back and hardware is also quite neat. It would mean a lot to mean if any of you could help me out.

[rpdom]

The wattage of the resistors just needs to be enough to handle the power that will be going through them. This will be very little for an LED being run from 3.3v, so 0.25W or above is plenty.

Looking at that site, "0,5 W koolfilmweerstanden 330 ?" (I think the ? is supposed to be an Omega symbol meaning Ohms), so that is a 0.5W 330 Ohm resistor. I'm guessing "koolfilm" means "carbon film", which is a standard resistor. (I just googled, and I was right - that's the only bit I had to look up). Use the standard Ohm's Law formula for LED resistors to work out what value you need.

The IDC headers come in two halves, one half has all the pins and connections in, and the other is used to clamp the cable in place. Place the cable on the "teeth" of the connector half, put the top half over it and push them together evenly and firmly (might be best to use a vice or workbench for this, but I've made do with all sorts of methods, including treading on them in with shoes. There are probably videos on youtube on how to do this.

The male header then plugs into the female header.

[E27006]

You can easily find and buy LEDS which have the correct size of resistor incorporated into the semiconductor for a typical voltages of say 5V dc or 12V dc.

One less component to source and clutter the circuit board (the external resistor) and one less calculation!

Here is such a link to such a device:
http://www.maplin.co.uk/5mm-5v-leds-35775

[Dreeass]

The wattage of the resistors just needs to be enough to handle the power that will be going through them. This will be very little for an LED being run from 3.3v, so 0.25W or above is plenty.

Looking at that site, "0,5 W koolfilmweerstanden 330 ?" (I think the ? is supposed to be an Omega symbol meaning Ohms), so that is a 0.5W 330 Ohm resistor. I'm guessing "koolfilm" means "carbon film", which is a standard resistor. (I just googled, and I was right - that's the only bit I had to look up). Use the standard Ohm's Law formula for LED resistors to work out what value you need.

The IDC headers come in two halves, one half has all the pins and connections in, and the other is used to clamp the cable in place. Place the cable on the "teeth" of the connector half, put the top half over it and push them together evenly and firmly (might be best to use a vice or workbench for this, but I've made do with all sorts of methods, including treading on them in with shoes. There are probably videos on youtube on how to do this.

The male header then plugs into the female header.

Thanks for the information, I have edited my note and added correct link of the breadboard. I'm trying to follow this video which tells me to use 2k Ohm resistors and I don't manage to find them that high so I should be fine with 2x976 Ohm resistors as long as I arrange them in series.

About the LED's, the Pi needs 5V but do I also get 5V from the GPIO? And the female headers, I have added a link to them. So to clear it up for me, I just have to 'insert' the male headers from the GPIO of the Pi into the female headers and then run my wire through this?

[rpdom]

2k resistors http://www.conrad.be/ce/nl/product/4207 ... -k-06-W-1- Metal film, rather than carbon. Slightly more stable if anything, but the difference is not important for this use.

The GPIO will output a maximum of 3.3V and any inputs shouldn't be above that voltage. You should design your circuit to run at a maximum of 3.3V where connected to the Pi.

The pi is supplied with 5V, but most of it runs from 3.3V, 2.5V, 1.8V and lower from regulators on the board and in the chips.

[Dreeass]

2k resistors http://www.conrad.be/ce/nl/product/4207 ... -k-06-W-1- Metal film, rather than carbon. Slightly more stable if anything, but the difference is not important for this use.

The GPIO will output a maximum of 3.3V and any inputs shouldn't be above that voltage. You should design your circuit to run at a maximum of 3.3V where connected to the Pi.

The pi is supplied with 5V, but most of it runs from 3.3V, 2.5V, 1.8V and lower from regulators on the board and in the chips.

Thank you very much, just a little question about the LED's, the ones I chose are 2.2-.2.25V but let's say I put 3V through the LED. How long would it take to break? Just precautions and how bright will it be when I put 1 or 1.5V through it? Is there a formula to calculate it?

[FTrevorGowen]

Thank you very much, just a little question about the LED's, the ones I chose are 2.2-.2.25V but let's say I put 3V through the LED. How long would it take to break? Just precautions and how bright will it be when I put 1 or 1.5V through it? Is there a formula to calculate it?

2.2 - 2.25V is the LED's typical "forward voltage drop" when they are conducting and emitting light. The actual voltage and their brightness will depend upon the amount of current flowing, typically 1 to 5mA. So, if you're "supplying" 3V and can also provide 2mA of current the series resistance needed will be:
(3.0 - 2.2) / 0.002
ie. 400 ohms
In practice 390 ohms or 470 ohms (typical "preferred values" from the "E12 series) could be used, the LED being slightly less bright in the second case. LED's can be "broken" by too much forward current or, being diodes, by a too high reverse voltage (when they do not emit light).
Trev.

[Dreeass]

Thank you very much, just a little question about the LED's, the ones I chose are 2.2-.2.25V but let's say I put 3V through the LED. How long would it take to break? Just precautions and how bright will it be when I put 1 or 1.5V through it? Is there a formula to calculate it?

2.2 - 2.25V is the LED's typical "forward voltage drop" when they are conducting and emitting light. The actual voltage and their brightness will depend upon the amount of current flowing, typically 1 to 5mA. So, if you're "supplying" 3V and can also provide 2mA of current the series resistance needed will be:
(3.0 - 2.2) / 0.002
ie. 400 ohms
In practice 390 ohms or 470 ohms (typical "preferred values" from the "E12 series) could be used, the LED being slightly less bright in the second case. LED's can be "broken" by too much forward current or, being diodes, by a too high reverse voltage (when they do not emit light).
Trev.

Thanks, this will definitely put my knowledge from school into practise.

Currently I was looking for a power adapter and thought 2A would do and after some time I came across some USB powerbanks and I know that it needs an output of 5V and 2A. But I don't know anything about how it is stored (Li-ion for example). Let's say I have a USB powerbank with a capacity of 5A, how much does the Pi take and stuff. I don't know how this works, could someone explain it to me?

[btidey]

The Powerbank is effectively a battery and will have a capacity rating in Amp-hours or milliAmp-hours. What that tells you is how long the battery will last when a particular current is drawn from it. So say you have a 5A-hour (5000mA-hour power bank) then that would last for 1 hour if you draw 5A from it or 10 hours if you draw 0.5A from it, or 100 hours if you draw 0.05A from it.

The Raspberry Pi (model B) on its own doing light work will be drawing 300 to 500mA and so would be lasting 10 to 15 hours on a 5A-hour battery. But you also have to take into account any extra current being drawn by any USB peripherals you have attached or anything you have connected to the GPIO power pins. Keyboards, mice and wifi dongles vary quite a bit. Efficient ones could be adding just an extra 100mA and not drain the battery much faster.

If you really want to know up front how long batteries are going to last then it is good to use a multimeter to measure how much current is being drawn from the battery when you have everything attached.

[Dreeass]

The Powerbank is effectively a battery and will have a capacity rating in Amp-hours or milliAmp-hours. What that tells you is how long the battery will last when a particular current is drawn from it. So say you have a 5A-hour (5000mA-hour power bank) then that would last for 1 hour if you draw 5A from it or 10 hours if you draw 0.5A from it, or 100 hours if you draw 0.05A from it.

The Raspberry Pi (model B) on its own doing light work will be drawing 300 to 500mA and so would be lasting 10 to 15 hours on a 5A-hour battery. But you also have to take into account any extra current being drawn by any USB peripherals you have attached or anything you have connected to the GPIO power pins. Keyboards, mice and wifi dongles vary quite a bit. Efficient ones could be adding just an extra 100mA and not drain the battery much faster.

If you really want to know up front how long batteries are going to last then it is good to use a multimeter to measure how much current is being drawn from the battery when you have everything attached.

Thanks for explaining it to me, I haven't got my Pi in the mail yet. In the meantime the Evernote note is kind of my shopping cart so I got everything when I get my Pi.