Intro: My Portable Workstation
This is my portable work station for small electronics hobby building. I will include a 12 Volt power supply from SLA batteries,a Dremel(knockoff), soldering iron, rechargeable battery, cigarette lighter outlet, voltage display, wall wart to recharge the batteries, a helping hand, and a way to heat-shrink without AC110V or Butane Refills, and some small hand tools.
The complicated part is a heat shrink device with no butane or AC power.
The rest is mostly cutting and fitting it all together.
Step 1: Acquire Box and Measure
Straight forward first step to make a portable workstation you need the box to take it with you, in this case I am using a metal skin from a https://www.hi-line.com/cabinetry/parts-drawers-r... This bin is 12" X 18" X 3". Hinged with a a latch on the front. I am using this because we determined at our shop that the removable boxes were getting in the way of the plastic liners that actually hold all the parts, this works for us because we are not trying to carry the boxes and their contents anywhere. Score for me, we now have a gang of these box skins that we can use for other things such as a portable workstation.
Step 2: Gather Your Parts and Tools
List of materials:
2 - ES7-12 battery (http://www.batteriesasap.com/657.html $18 each)
2 angled brackets for battery securing (Free to me, but cheap to make, just take a piece of 22 gauge 1" strip and cut the length you want and put a 90 degree bend in it)
Cigarette lighter for Automobile (Left overs from project, cost approximately $8 each)
10 Watt Resistors various ohms Radioshack ($1-3 per pair, I used (2) 1 ohm and (4) 10 ohm)
Helping hand (SparkFun https://www.sparkfun.com/products/9317 $9.95)
Hinges (free from a found item)
plywood 3/8" smaller than box will trim to fit, (Free cutoff from previous project)
Various nuts, bolts and screws (maybe $5 - $10)
12 volt 20 Amp circuit breaker (maybe $5 dollars)
cheap voltage monitor from Amazon(< $10)
12V 30 Watt DC Soldering iron on Amazon for about $10
screwdriver with multiple bits, $3 at Targets dollar area
knockoff mini Leatherman style multi-tool, also $3.
wire varied gauges and colors
relay spdt 30 amp
push on/push off switch
Duct Tape and Electrical tape
Total - approximately $106 minus the box.
I reused a lot of things I already had so this total for me was less, mainly because I already had the batteries, dremel, and resistors.
Now for the list of tools:
drill bits / unibits
hand wrenches and screwdrivers
Air Sander and cutoff tools, or Dremel
Step 3: Adding Hinged Workshelf
Here is how I set up hinges and such when multiples are used.
Put the hinges next to the area that will have the shelf attached to it, I chose to put it on the right side. Mark the area that needs to be cut out so that the hinge can clear the side when it is opened up. Trim out the area. I chose to use Dotco style side cutter with a 3 inch disc I believe, but I only cut the vertical slots, and then bend the metal over to help reinforce the area since it is thin gauge steel. Then I used 1/4" self drilling - self tapping screws to temporarily place the hinges and plywood with the cordless drill.
I connected this together in this order. I put the first hinge in, and attached it after carefully making sure that the wooden shelf was where it needs to be for clearance. Then after temporarily placing the hinge, attach the plywood to the first hinge. Then attach the second hinge to the plywood and attach that hinge to the box. Once these pieces are temporarily attached test the fitment, and add more screws till it is attached as well as that will allow. Then you can drill the holes for all the mounting hardware. I use the screws because they are quick and easy to use, and then I replace them with 1/4-20 bolts after drilling the holes to fit, not always necessary when using similar sized bolts to the screws. The bolts for the plywood are 1/4-20 carriage bolts. The plywood needs to be cut down to fit in the box with the batteries in place 11 1/4" X 12 5/8".
This measurement is 3/4" less than the box width, and the length allows for the 2 batteries to be mounted and not interfere with the shelf. after cutting the plywood to fit, sand and make it nice, and reattach. You could also paint the plywood now if you prefer, then attach.
I placed the batteries in the box at this step to make sure everything fit.
Step 4: Battery Securement
These angled brackets are 1.5" X 3" X 3/4" about 20 gauge. I placed 1 battery in the corner and placed the bracket in place and used a self drilling self tapping screw to secure it. Then I moved the battery to the second position, and placed the second bracket with a second screw in it. I then replaced the screws with machine screws, and trimmed them to fit. I added foam cushioning to protect the batteries.
Step 5: Add Power In/out Port (i.e. Cigarette Lighter)
Drill the appropriate sized hole for a Cigarette lighter socket. For mine that was a 1" hole, I used a unibit/Drill All/Step Bit depending on who you ask. I then used a 90 degree dotco sander to debur the inside of the hole. I then placed the socket in place, and am ready to wire it. Drill a hole for the Lamp and on of switch, place them in.
Step 6: Add Circuit Protection for 12 Volt Circuit and Power Switch
I added a 12 Volt 20 Amp auto resetting circuit breaker to the box. In line before the circuit breaker is a relay controlled by a switch mounted to the front of the box(https://www.sparkfun.com/products/9808), The on Lamp is attached to the cigarette lighter. All other powered items can be attached to the circuit breaker. The 2 batteries are hooked up with .25" spade terminals, and the circuit breaker is attached with .125" ring terminals. I also grounded the batteries to the case so that the whole box is negative charged as an automobile would be, since a great deal of my projects are automotive related.
Schematic for connections is at the end of the instructable.
Step 7: 12 Volt Charger
This wall wart is a unregulated DC 12V supply for the knockoff Dremel I included in the kit. Since I have a 12 volt DC power supply in the box I didn't see any need to try and step up to 110 to run this wall wart to use the dremel,,, seemed wasteful, so I repurposed this wall wart to charge the (2) 12V 7Ah batteries when I am close to AC power so I can be fully off grid working on projects out and about. To make this into a charger for a 12V lead acid battery, all you need is a high power (10 Watt or more) low resistance (there are calculations for this, but I went with a 1 ohm resistor) in series with the power lead from the charging source to the battery being charged. (Do this at your own risk, all the standard rules apply I am risking it myself, and I am ok with that knowing what I know, but I take no responsibility for others doing the same thing) This is not the first time someone has made a poor-mans trickle charger for a lead acid battery.
The battery charger was functioning while I was working on the next portion, and the cheap voltage monitor from Amazon(< $10) was showing a rise in voltage while I watched it for 1 hour from 12.4V to 12.8V. Don't leave this hooked up without monitoring it unless you did the right calculations and understand how it is working. For my use this setup will work. I never intend to leave the charger going while I am not around.
Step 8: Knock Off Dremel
After using the power supply from this dremel type tool, we need to get ready to use it. Take the power leads and attach them to the battery supply. I made these connections and the ones from the wall wart to the battery with quick disconnect .25" spade terminals that are oriented so that the wall wart can be reattached to the dremel tool.
Step 9: Inner Storage and Guts Covers
The shell that I used also had a liner with parts dividers, so I am reusing it, sort of. I am going to trim it down in height so it will fit under the folding shelf. This requires measuring the depth in the shelf goes, so hook the plywood on the underside and measure to the top of the skin. I laid the insert on the progress so far, so I can get an idea of what has to be removed to make it fit. On this set up I will be able to use 2 full sections of the adjustable storage once the bin is trimmed short, and notched for the hinges. Band saw time, I use a band saw to rough cut it down, and then a side cutoff wheel to make it shorter and notch the hinge area. Based on the measurement of 3/4" depth I will cut the storage compartments to allow the shelf to fold in. After I finish cutting the storage area, I will use the rest of the tray/insert to cover the power connections and guts on the battery area.
Step 10: Soldering Iron
Not much to say here, I found a 12V 30 Watt DC Soldering iron on Amazon for about $10 after shipping, not expecting much, but it actually works ok, not great but worth $10, with a variable voltage supply it could be better, but I don't need it yet, I am only using it for a few solder joints on the go, and it works well for that. I did cut the cord to add a switch to make the tip grounded for delicate electronic soldering, but that was not that big a deal to do, and if you want instructions I can make them with requests.
This soldering iron plugs right into the cigarette lighter I installed on the front.
Step 11: Heat Shrink on the Go Without AC 110 V Available.
I have always wanted to have a way to heat shrink wires out and about. Lighters while they work are not the best solution and most electronics knowledgeable people will tell you that an actual flame will actually cause the heat-shrink to fail prematurely, I have experienced it and will never use that as a means to heat shrink a wire. I have also had issues in some vehicles when the heat gun was causing the factory wires to char while the heat shrink was barely shrunk. Also not good, so I was looking around the table while starting this project and I found some 10 Watt resistors, and remembered how hot those resistors can get, so here is the result in crude form at first, needs a switch, and some real lead management, but proof of concept works. I took 2 1 ohm 10 watt resistors, and 4 10 ohm 10 watt resistors and set them up like in the drawing.
I tied 4 10 ohm resistors in parallel, and put the 2 1 ohm resistors in series with the now 2.5 Ohm resistor pack. making the total resistance 4.5 ohms, and this gives a total current draw of 2.666 Amps, at 12 volts. Initial test showed that the heat shrink was not shrinking with this setup, so I moved the power over to the 2nd 1 ohm resistor making the total current draw 3.43 Amps, and the resistors were still not getting the heat shrink hot enough, so I went to just using that 2.5 Ohm pack making current draw 4.8 Amps. I know that this is overdriving the resistors, but I then after they had warmed up moved the 12 volt lead back to the 1st 1 ohm resistor, and it maintained the heat for a while, so with a select-able switch and power lead configuration, you could use this as a heat shrink device, as long as your pre-warm time is not too long, and you pay attention to it.
The heat shrink tube on the go... works, I soldered the leads to the resistors, added a metal tube in the middle, and added heat shrink around the whole thing. In its last test, I was able to heat shrink a 10 gauge wire in less than 3 minutes from cold to warm, not fast, but gets the job done. I still need to add some switches.
Switch 4 position rotary switch, this will allow me to select which resistors are energized. I have it wired so that the first position on the switch is off. Next is High Heat (only the parallel resistors). Third is Medium Heat (parallel and 1 ohm resistor in line). Last is Low Heat ( 1 ohm resistor, 1 ohm resistor, parallel resistors).
Step 12: Cleaning It Up and Finalization
The first picture is of the power and protection area, that is covered during normal use.
The second picture is with the cover on the power area, and the others are pictures of everything in the case. Will try making it more organized for better photos, and still need to paint it.
Step 13: Add the Little Things (from Targets Dollar Area)
The first picture is a screwdriver with multiple bits, $3 at Targets dollar area. Not high strength, but will work for many light duty used. It uses non standard 1/8" bits, but for small things will work fine.
The second picture is a knockoff mini Leatherman style multi-tool, also $3.
Step 14: Paint
A project like this would not be complete without a paint job. I chose to keep the flag, and paint only the red parts and the advertisement from the parts supplier. Mask off the area after cleaning the surface. then if you are like ma and can't get it right the first time, go back with an exacto knife and cut the excess tape so that the lines are nice and straight. Then sand around the area that is masked off, and clean for paint. I chose black as my paint color. I then removed the tape and clear coated the whole thing. I painted this in 25 minutes, and it turned out ok.
Step 15: Schematic of Electrical Components.
Attached is the schematic.
Step 16: Done
Aside from a better wire management solution, it is done. The switch in the last pictue is the switch for the heat shrink device.
I used all of the tools in the box to help make the box at some point or another, I have no clue the actual length of time to build this, but I would guess around 15 hours. I built this on lunch and breaks at work mostly over the last 2 weeks.
All in all a fun project, and I still have more boxes that I am thinking of making an electronics prototyping area in with many voltages, and component storage. Maybe an onboard Propeller, Arduino, and others as well.