First Labby help needed

[jordan6194]

I am preparing to build my first labby but was hoping some of the more experienced on this forum could check for any errors or red flags i might have missed :thinking:

attached is the circuit diagram i have constructed, which lead to a few questions, but first i will give a detailed component list:

###########################################
Power Supply: regulated power adaptor (5V or 9V) max draw 2A
Key switch (safety): rated to 4A 28V DC
Operating switch: rated to 5A 250V AC
Fan: EITHER (5V 8CFM) OR (12V 19.3CFM)
LED: 2V at 20mA
Resistor: value depends on power supply. R=(Supply-2)/0.02
X-Drive v7 Mini: bought from flamingpyro, input range 2.5-9V, ouput 1A
Oclaro 700mW diode: bought from DTR, input: typ 900mA max 1.1A
Flyback Diode: EITHER (1N4004 400V @ 1A) OR (1N5404 400V @ 3A)
###########################################

And now, questions from a noob

1) I thought to put the flyback diode in to protect against any back current coming from the fan (i am unfamiliar with fan circuitry), but is it necessary?

2) I am having trouble choosing which power source to go for. the 5V would be safer for the driver but would mean a smaller, less powerful fan.
On the other hand, the 9V is right on the limit of the drivers input (not sure what the implications here would be) but would mean i could run a more powerful fan, a little under voltage unfortunately.

3) The wire i have is rated to 1.5A, is this cutting it a little too close or should i be okay?

4) There may, and quite likely is, other errors ive missed so please educate me and spare a poor diodes life :angel:

Thanks a lot guys
:thanks:

-------------------------EDIT--------------------------------
P.S That circuit was drawn using DoCircuits, an online tool. If any of you pros know of much better tools feel free to suggest

 

[Cyparagon]

Flyback diode should be in parallel with the fan - reverse biased. It may not be needed depending on what kind of fan it is, but it doesn't hurt.

Wire is cheap or free. Why are you using something so tiny?

Why the xdrive? Space and efficiency aren't a concern, so why not lm317? lm317 can take 12V no problem.

You could have different voltages for the fan and driver as well. There are many correct answers.

You'd ideally want to use a different indicator lamp color from the laser color to make it visible when/if safety goggles are used. Your 2V drop suggests you're planning on using red. Using a red light to tell the user there is a red light present is silly.

 

[jordan6194]

thankyou for the quick response,

i think i understand what you mean about the diode, taking the path of least resistance, it would then return any stray current back to the cathode end of the fan rather than the driver, correct?
The fan is a Sunon (sleeve type?)

i was using the wire just because its what i already had, but thats a good point ill source out thicker

i have completed a driver with an lm317 before (but on a much lower power build) I chose the x-drive because it was suggested to me not to do too much myself before gaining experience with the more powerful diodes

OOOHHH of course! you are referring to voltage division? i cant believe i didnt think of that! i have redrawn a circuit using a 12V supply this time and used a pair of resistors and voltage division theory to deliver 7.05V to the driver.

the LED is a 5mm green bezel, safety goggles are a must of course

Does this look more appropriate now? and thank you so much for your help!

---------------EDIT-----------------
sorry i have the two series resistors in the diagram the wrong way around, although this would still work, only supplying 4.95V instead

 

[Cyparagon]

OOOHHH of course! you are referring to voltage division?

No, voltage dividers are a bad choice for anything other than very low currents, because they waste a lot of power and/or the voltage will sag a lot. I was thinking more along the lines of a 7809.

Realistically, the heat of this diode will be tiny, and 20cfm is way overkill. I've got a 130amp power supply that uses a 20cfm fan. You'd be fine with <1cfm. Running everything at 9V or using the 5V fan and running everything at 5V is probably the simplest way to do this.

 

[jordan6194]

yes youre right, ~1A current going through a resistor would quickly add to a lot of dissipated heat :cryyy: i had a look over the data sheet for the lm78XX series, useful stuff to know so thanks for bringing those to my attention.

i think your second suggestion is the way for me to go being the simplest a 5V supply and fan is easy to get and simplifies the circuit a LOT!

130A! woah! okay great that makes me much more confident, after reading so many horror stories about cooked diodes i wanted to be sure.

ill post my final circuit diagram (and pray there arnt any more mistakes)

Cheers for your knowledge cyparagon i cant wait to get started!
:thanks: :thanks: :thanks: