Need opinions on relay launcher front panel design (WARNING: HUGE IMAGE)

Well, I've almost finished my sophisticated ATmega8 relay launch controller. That's what's left from the to-do list:

* Finish sanding the edges of the relay part's box
* Make a bottom for the relay part's box
* Make a front panel for the relay part's box << that's the one I made the thread about
* Make a box for the launch-button part

Click to expand...

The LEDs are in place, so I can only swap them in the AVR source, not move them around
As for the rest, do you think this front panel looks good or it needs changes?
image removed by user
P.S. The "hold time" grey square is a four DIP switch array and the "Check for Igniter?" grey circle is a regular switch,

DexterLB said:

Well, I've almost finished my sophisticated ATmega8 relay launch controller. That's what's left from the to-do list:

*Make a front panel for the relay part's box << that's the one I made the thread about

Click to expand...

The LEDs are in place, so I can only swap them in the AVR source, not move them around
As for the rest, do you think this front panel looks good or it needs changes?
P.S. The "hold time" grey square is a four DIP switch array and the "Check for Igniter?" grey circle is a regular switch,

Click to expand...

By relay parts box, I assume this will be out by the pad.

I don't know what value added the hold time will give you but it is a neat feature and probably fun to build. I would probably leave it in the As long as the launch button is held mode.

I don't see an arming switch. I don't think the box should be armed remotely. Just for safety reasons, the person hooking up the igniter should be able to arm and disarm the relay box.

By Fuse Problem, I also assume that is the fuse between the battery and the box. Not sure you need a LED for that, but what the hey!

I also assume the Battery Flipped LED is there because you need the correct polarity for the DC circuits. Will the relay still work from the remote with the battery polarity swapped? Not sure you really need this either because the Power LED shouldn't light if the polarity is swapped. Again, neat feature.

The Check for Igniter switch, I would suggest a momentary switch, probably a pushbutton. I have a regular toggle switch for that on a controller of mine and although I know how it works, it did confuse a few others that thought the switch had to be on to make the controller work.

Just my :2:

Assuming that the 'Battery Flipped' indicator is only there to keep the polarity of the power source to the electronics correct, you may want to consider adding a bridge rectifier to the circuit. Since the igniter doesn't care what polarity the power is, you don't have to worry about it that way.

Handeman said:

By relay parts box, I assume this will be out by the pad.

Click to expand...

Yes, it will be out by the pad. It contains the relay, the PCB with the microcontroller and lots of wires.

I don't know what value added the hold time will give you but it is a neat feature and probably fun to build. I would probably leave it in the As long as the launch button is held mode.

Click to expand...

I made this feature to prevent "Hmm, it doesn't want to launch. Let's try holding the launch button for 30 seconds before going to check what the problem is, shall we?" situations, which usually have damaging consequences :shock:. And, what do you mean by "value added"? Sorry, I'm not very good at English...

I don't see an arming switch. I don't think the box should be armed remotely. Just for safety reasons, the person hooking up the igniter should be able to arm and disarm the relay box.

Click to expand...

That's a great idea! I did intend to arm it remotely only, but now I'm going to add a second arming switch in the relay part.

By Fuse Problem, I also assume that is the fuse between the battery and the box. Not sure you need a LED for that, but what the hey!

Click to expand...

In my opinion an LED that indicates a problem is always good :cyclops:

I also assume the Battery Flipped LED is there because you need the correct polarity for the DC circuits. Will the relay still work from the remote with the battery polarity swapped? Not sure you really need this either because the Power LED shouldn't light if the polarity is swapped. Again, neat feature.

Click to expand...

Yeah, I've had several cases with devices that I place a battery and nothing happens, and I think I've reversed the polarity, and it takes me lots of time to find out that it's not the polarity and is something else instead... and vice-versa. Another LED that will most probably be never needed

The Check for Igniter switch, I would suggest a momentary switch, probably a pushbutton. I have a regular toggle switch for that on a controller of mine and although I know how it works, it did confuse a few others that thought the switch had to be on to make the controller work.

Click to expand...

I don't know about the others, but I myself like toggle switches. :bangpan:

Many thanks for your reply!

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How about the colours of the front panel? Do you think it needs more colourful fonts, background gradient etc, or less colours?

Len_Lekx said:

Assuming that the 'Battery Flipped' indicator is only there to keep the polarity of the power source to the electronics correct, you may want to consider adding a bridge rectifier to the circuit. Since the igniter doesn't care what polarity the power is, you don't have to worry about it that way.

Click to expand...

I wanted my controller to support 9V input as well as 12V, so if I add a rectifier that's two active diodes at the same time --> 0.7*2=1.4V dropout --> the voltage at the input of the LM7805 will be 7.6V that's 2.4V above the output voltage and the recomended is 3V. So I'll have to use 4 SCHOTKY diodes that have a lower dropout voltage, and I have only two high-power schotky diodes, and local shops don't have high power schotky diodes so I have to purchase them online and that gets too complicated

Look into the 0 volt drop "transistor style" diodes.

Bob

bobkrech said:

Look into the 0 volt drop "transistor style" diodes.

Bob

Click to expand...

Where can those be found? My Google search hasn't come up with anything along those lines.

TWRackers said:

Where can those be found? My Google search hasn't come up with anything along those lines.

Click to expand...

AFAIK there is no simple drop-in replacement for a diode based on a transistor but, depending on your application, you can find a circuit with an MOSFET which behaves like an diode. These circuits are often called "ideal diode". They may contain a dedicated controller which controls the MOSFET. Examples include the LTC4413 (integrated FET) or LTC4357 (external FET).

A simple reverse voltage protection can be built with only a single MOSFET. This concept can be extended to a full bridge rectifier..

All these examples exploit the body diode of the MOSFET by putting it in "backwards" (drain and source switched compared to typical application). This allows the circuit to power up until the gate source voltage is big enough for the MOSFET to become conducting thereby reducing the voltage drop.

Reinhard

Reinhard is correct, and found the EDN reference I was looking for. The 'Ideal Diode" is usually a MOSFET type device with a very low turn-on voltage and virtually no reverse current.

An example is found here. https://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1142,C1079,P85544

Ideal diodes can also be made with certain single-ended OP amps as well. Again basically a half-wave rectifier with no negative voltage output.

A Google search on ideal diodes will get you the info you need.

Bob

:w: finally finished the part that is near the rocket.

Here are some pics:

Bottom without lid:

Bottom with lid :

Connected to the part with the buttons (it hasn't got a box yet):

The fuse:

and the entire gallery

Now all that's left is print the front panel, stick it and make a box for the part with the buttons (Someone please suggest another word for 'the part with the buttons')

So, what do you think?
I'll be posting circuit and firmware shortly.

P.S. if the images don't show up it means my server is off. It's typically on during the day, CET