# Tag Info

3

This is a multi collector transistor. More common is the multi emitter transistor used in TTL integrated circuits.

0

Digikey's "Scheme-it" software looks similar. You can try it for free at http://www.digikey.com/schemeit. That's the closest I could find, but as the others said you can create schematics in this style very easily with any drawing program. MS Paint is a very common one, and gives you the freedom to draw any component the way you want it.

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Other than the internal shading (which I don't like), those are common schematic symbols which could come from any electronic CAD program.

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There are tons of options (and opinions about those options) for this. I recommend you install and use Eagle CAD to design your (non-commerical) schematic and PCB. Once your design is complete send the CAM files or Eagle PCB files directly to OSH Park.

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It really depends on the designer. The schematic symbol is something that is visually useful for you. A jumbled set of pins will have the same functional effect as a set of pins that is more organized. It's entirely up to you. For instance, when I create a component, about half the time, I'll create the symbol as what's presented in the datasheet. It ...

1

I generally want signals to flow from left to right, so I put inputs on the left of the box, and outputs on the right. Power connections (if shown) go on top, and power (again, if shown) on the bottom edge. The box must, of course, be tall enough to show all the pins, but only needs to be wide enought that the pin names don't overlap. I would usually put ...

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I haven't done this is a very long time (more than 10 years now) but what I used to do to draw cabinet wiring schematics is to use a PCB design tool and build my own custom component library.

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It will work with the values and ratings shown, however the output current will be limited by the regulators to (at most) 1.5A or by the thermal limit set by the heatsinks, power dissipation and ambient temperature. If you want to use the full ~2.5A capability of the transformer you'll need significant modifications to the regulators- something like the ...

3

I'll assume this is the schematic you are referring to: The four little hollow "C" shaped things are sliders that short two pins together. They are all depicted in their left-most positions, but can be moved to three other position. Think of them as little shorting bars that all move together left/right. This is showing you that the switch has four ...

7

Those parts in the middle are rigid and are attached to the slider so they move together. They have 4 positions and will short various pins depending on the position. As you can see, the blacked-in dots that go to double contacts can be considered the common of each pole and they will each be connected to one of the four adjacent non-blacked-in dots ...

1

The four elongated horseshoes are the shorting bars. As they move along they short different throws (the hollow circles) to the poles/common pins (the filled circles). Since this is a 4P switch, all four shorting bars move the same distance at the same time. The position of the circles in the schematic reflects the locations of the physical pins on the ...

2

That bead seems unconnected by default, through solder bridge 57, which I suspect is normally open. If 57 is closed, it connects Vdd to AVdd, but prevents noise from Vdd hitting the analog ref by increasing high freq impedence.

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You don't need the 1N4004 diode shown in the circuit you linked to ("Wiring SSR with Arduino"), since SSR's are not inductive so no flyback diode is needed. Also you don't need the transistor since according to the datasheet you linked to for the relay, it will operate over a range of 3-32v, with a constant current of 7.5 mA for the LEDs (thanks Dwayne). ...

0

A few things to improve on for the updated Schematic: 1) The LM556 should not have +12 inputs (eg.: RC and Reset pins) while being powered from +5v, possible burn out. Much better to keep all inputs and power at the same supply level. 2) The four switching transistors (Q5,6, T9, and unmarked) need to have current limiting resistors at their base pins. ...

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If Orcad makes a connection between two crossing wires it puts a little dot there so you know. They call it a junction I think, so if you don't see the dot you should be ok. If you want to make them connect there is a button to add a junction. It's in your standard tool bar, looks like a cross with a red dot in the middle. You can click that then use ...

3

I use orcad 16 and if you drag a wire that crosses another wire where that wire connects to a component it will justifiably make a connection. Just ensure that dragged wires don't intersect at component terminations.

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For R19 you should have the center tap pin going to the + motor, then ground the - motor pin separately. The other R19 pin can be connected to the center tap (or just left open). Your original connection setup could have shorted the +12 to ground. Note that using a resistor in series with a motor like this will not be very efficient. If the motor is a ...

0

Q5 and the unmarked transistor below it are connecting logic pin outputs to ground or + supply, that is not usually a good thing to do. If you want to over power a logic gate output with a transistor you should use a resistor directly after the gate output. That limits the current out of the gate. (You may need to explain the logic here to get a better ...

3

This should really be a comment, but I need to show a schematic. All places where a transistor (or photo-transistor) drives a logic input should be something like this: simulate this circuit – Schematic created using CircuitLab You don't need the resistors you show between the transistor collectors and the gate input, but you do need pull-up ...

3

Are there any silly shorts that I should address? Yes. For example, all of the inputs to your logic (IC2 and IC3) are connected to the same node, the one connected to the collector of Q7. I'm guessing that this isn't what you really wanted, but of course, without a functional description of the board, it's impossible to be sure.

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1. Show Your Work A Schematic Diagram is intended to be the documentation of a circuit. As such, I highly recommend including any simple equations that may be used. This includes LED current calculations, filter corner frequencies, etc. Show your work, so that the next guy who has to read the schematic can check it easily. 2. Indicate UART Direction Since ...

2

I have often used keynote (you may also choose to use PowerPoint). This has the advantage of allowing screen caps of simulation software such SPICE GUIs and such. Really key for me is the ability to drop in snippets from data sheets and mark them up so the relative importances in my design decisions show up. I can also include photos of early circuit ...

2

I keep a design notebook, and carefully document needs/wants. For the earliest prototypes, I'll go through part selection, taking notes on all the real decisions. For subsequent changes, I use a fairly formal FMEA process, documenting which need is not being met so as to justify a change -- because obviously, if there is no unmet need, there's no need for ...

3

For many of my smaller projects, I've generally been placing a simple green label and border around sub-circuits. For larger projects, some eCAD software allows you to build from a block diagram down, where each sheet further describes a single block. There's an art to decomposing any problem, and managing the tradeoffs (that's engineering IMHO). Where ...

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I personally go the old-fashioned route: I have a design notebook where I write down absolutely everything about the design decisions I make. Especially component and value choices, current calculations, power supply calculations, everything. I also document software/firmware decisions and notes on timing and resource usage. Each notebook has a contents ...

4

I do a lot of quick-turn design and I have to say: annotating the schematic is by far the most convenient thing. It's rare for any of my designs to be more than 2 or 3 A4 sheets, so the amount of design decisions is limited. A lot of design decisions are pretty much automatic; I don't need to list reasons for every single part. Just one or two main parts and ...

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You could go back and update the design spec with this information. Or take the spec and create a lower level spec where you describe in more detail what you are going to do and why, ideally before you start schematics :). Then update as you go along and archive with the schematics. Answering questions below: Well what we usually do is start with ...

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You have to use the NAME tool now . Just type: name MY_NEW_NET_NAME_HERE into the command box at any time then click twice on the net you want to rename. You can rename two nets to the same name doing this and they become logically the same NET. The label tool simply visibly shows what the underlying NET name is.

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The correct way to do this is with variants, as others have pointed out. Do not use the 'Type' property. For every project I have a variant named "Only Populated Components" which makes it super easy to DNP components. Not populated components should NOT appear on the BOM, as this will indubitably lead to questions from the CM. They should also not appear on ...

3

It will discharge when the +Vcc is switched off. The left plate is then connected to the ground via the power supply. The RST input then becomes -Vcc with respect to the ground and discharges via the resistor. +Vcc present: +Vcc not present: When the capacitor is charged the left plate is +5V with respect to the right plate. Since the +5Vcc power ...

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The RC network circled in black is a power on reset circuit. I have attached a figure from an ST application note Simple Reset Circuits for the ST6 It is oppposite of the picture you attached, as this ST62XX is reset low instead of high voltage on the pin. The purpose is to keep the device in reset until power rail has come all of the way up. The RC ...

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Is the pin that the RC circuit in the black circle connects to called "RST"? If so, that RC circuit provides a power-on reset pulse - when power is applied, the capacitor will pull that pin up to Vcc, then will be charged through the resistor, allowing the voltage on the pin to drop. The resistor in the blue circle appears to be a pull-up resistor to ...

2

This circuit (in the black circle) causes a pulse on the pin connected to it. If the capacitor is empty it starts filling through the resistor. As the capacitor fills with charge, the current through the resistor slowly falls, and the voltage on the pin also falls. Once the capacitor is full no more current will flow an there will be "0V" on the pin. I ...

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R1, Q1 and R2 make up a TTL logic inverter, where R1 limits the base current and R2 is the load. However, the output is between Q1 and R2, and it is not indicated by a pin in the schematic. The connector only connects to the supply rails. For what reason it is done like this, I cannot say.

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Looking at the circuit you posted, the transistor Q1 does not have a function. Activation/deactivation of Q1 does not cause: any information to reach CON2. influence of any kind on other sub-circuits you have shown If you think this is not so, you will have to show us more of your circuit.

3

You can download lots of libraries for EAGLE from their website, but it is often quite difficult to find a library containing the desired devices. Especially for very specialized parts, like the microcontrollers you use, often no library exists yet. Luckily, it is quite easy and straight-forward to create them yourself in EAGLE (citation needed). An EAGLE ...

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Altium doesn't have a lot of footprints, I've found. At least, unless you subscribe to their "vault" nonsense (\$). So, I make footprints all the time. Schematics are super easy to make. Create a new schematic library, then hit "Tools" -> New Component. now just draw a rectangle to represent your part, then place some pins (press P, then P again). The ...

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