Introduction: Portable Boombox
My first Instructables post... :)
I'd like to apologize in advance for my poor writing skills, English was never my strong point at school.
I work outdoors in the U.K doing Drystone Walling (maybe my next post) and nothing is better than a bit of music at work. I began looking through "site radios" and was shocked at the price and even more at the battery prices. I found that some had too many features or a slight gust of wind would be louder than their max output. Having a tendency to tinker with things and a love of DIY I thought I'd have a go myself.
After hours of browsing many websites and Instructables posts I was inspired by many others, I can't remember any in particular that I wanted to follow 100% and so just followed an idea I had in my head.
The Ammo box idea that 99% of people seemed to go for was a big inspiration but I thought I'd not be able to pack as much punch into a small box and rather than using a small mp3 module with awkward buttons I thought I'd (try) go for a simple as possible approach since some of my colleagues are very old school and dislike technology.
I regretfully didn't take as many progress pictures while making the project and didn't think about putting it on instructables until afterwards - maybe I could submit this into a competition and hopefully win a 3D printer or something that would help me make a mark 2 version of this. I will draw up some 3D images of anything I can't explain well enough with images.
I'll try and keep this post as simple as I can and assume that everyone has minimal knowledge of starting a project like this.
- Plywood - I bought one small sheet from Homebase (a British DIY chain). Nothing fancy, not even marine ply I think I went for 12.5mm thickness.
- Screws - Just get a selection, I hate reading some Instructables posts where everything is so precise. I think i used over 5 types/lengths of screws in this project just used bits and pieces I had lying about. Machine screws look good on the metal edges.
- Heatshrink sleeves - Buy a pack with various sizes/colours - I kept my Ground wires black, Positive Red and a colour for each speaker.
- A car stereo
- I used a Kenwood KMM-BT302 which I managed to pick up used for £29 on eBay. Bluetooth was important to me as when I get sick of UK radio stations I like to connect my phone up. DAB was not essential for me and the best thing to look for is something you actually need and not too complex.
- I would avoid cheap chinese stereos from eBay like the plague. Go with well known brand name.
- The wattage output is important to look at I know that mine can provide 4 x 50W max , I tried looking for the RMS (average) values but could not find
- Size, I went with Single DIN (I'm not sure if DIN is a worldwide term but single means like a normal size stereo and double DIN stereos are usually the type with big displays)
- Look at what your stereo provides if it provides a max of 10W per speaker don't go with a speaker that has an RMS (average) wattage higher than that.
- I went with 6.5" speakers as they are the most common, go with something that will fit what you need.
4S 14.8V BMS PCB Protection Board - I got one from eBay, no faults as of yet.
DC Barrel Male /Female
5 Pin DIN socket
5 Pin DIN cable
iMAX B6 balance charger - if you google this you'll see many a thread about fake vs. genuine chargers, I went for the legit one better to be safe than sorry
Soldering Iron - Don't need fancy stuff, any will do
Solder - Don't go cheap with this
6 Pin DPDT rocker ON-OFF-ON
4 Rubber feet - I bought little door stoppers from Wilko (cheap UK store)
Vinyl Wrap - I went for a dark green since I work outdoors out in rural areas I thought it'd be best not to stick out like a sore thumb.
Holesaw - Best way to get initial hole in for jigsaw
Sandpaper - various grits, higher the number the finer the sand
Metal file - for tidying profile cuts if your dremel skills are as bad as mine
Dremel with metal cutting discs - I used this to cut the metal profiles, use something more appropriate if you have
Step 1: Front Panel
Once you have purchased the many supplies for this project I found it best to focus on the front facing panel of wood first.
At the moment you will have a plywood sheet(s).....
- Lay your speakers face down on the wood
- Make a paper cut-out of the dimensions of the length and width of your stereo and also place on wood
These will be the main items showing on your front panel move them about until you are happy with spacing and location.
Once I had a suitable size to accommodate the two speakers and stereo I drew a rectangle on my plywood also allowing for a little more space around speaker holes for the speaker grills.
- Place your panel on your plywood sheet and mark around it with a pencil so you have your dimensions ready for the rear panel of your box
- Place your front panel in front of you and with a ruler or measuring tape mark the mid-points on one side.
- Draw along the midpoints to create a cross-hair on the front. I have included images made in a modelling program to show this better.
- Align the middle of your paper stereo cut out with the horizontal mid point and align the bottom edge of your paper stereo cut out with the vertical mid point.
- I create two more mid-points either side of the stereo cut out. Horizontally from left side of stereo rectangle to left edge of panel and right side of stereo rectangle to right edge of panel.
- The two points you have made in step 5 will be the centre of your speakers you can either place your speakers down on the wood and trace around or measure the diameter of your speaker then set a Compass at half (radius) and draw from that mid-point
If you have chosen to have USB ports like I did you will have 3 more holes below the stereo. One for powering the stereo, one for powering the USB module and then the third for the USB ports.
- Draw a line down from each side of your stereo rectangle to the bottom edge
- Mark a midpoint on each of these lines
- Draw a line joining the two midpoints
- Use your actual buttons and USB port to mark out the circles somewhere along this line
I cut my first panel out with a handsaw (I know not the best choice but,....it worked). I then sanded down any rough edges with a low grit sand paper.
For the speaker holes and stereo hole , I used a Holesaw to make the initial hole and then used a Jigsaw to finish.
The holes for the buttons and USB ports were cut with just a Holesaw
Sand rough edges.
Step 2: Side Panels
I made the holes in one of the side panels after originally putting the box together as I came up with an idea to make the charging easier.
The top left rocker switch shown in one of the images is a ON-OFF-ON DPDT rocker ( I have included an image example of how one would work). If I had thought of doing this before building I would have maybe considered putting it on the back panel or at bottom left of the side and moving the DC socket and DIN port along.
Sides I made were 180mm Width, 168mm Height
Cut and sand the sides.
I made the holes for the DC socket and DIN port with Holesaws and the Rocker with a Holesaw initially then a jigsaw and sanded the holes.
I will cover the electronics of the switches and ports in another step but for now cut out the holes.
Step 3: Back Panel
The easiest way would be to trace around the Front Panel you cut out in one of the earlier steps and then cut this piece.
The only hole in the back is the one for the aerial. This was approx 8mm diameter and I just used a drill bit.
Step 4: Bottom & Lid
The LID & BOTTOM measured 550mm L, 180mm W
Cut these from the rest of your plywood sheet.
Step 5: Time to Wrap It Up
Nope not the end yet.
Time for vinyl wrapping the wooden panels you have previously cut.
There are many wrapping videos on YouTube which will show you how to do this best.
I bought a roll of an olive green wrap from eBay there are many on there especially Carbon Fiber ones. I believe mine came with a little slicing tool which was useful.
I cut rectangles a little bigger than each panel and then cut them out of the roll. You can see an image in this section showing if the wrap was underneath the front panel.
I sanded the panels again and then wiped them in prep for wrapping.
I started to peel the rectangle and rolled onto the wood using my sisters hair dryer to help stretch over sides.
For each hole in the panels like the speaker holes, I cut small lines from about 2cm of the circumference of the circle to the middle of the hole then folded into the inside again using the hair dryer to help stretch it. I have created an image showing the lines I cut.
For the stereo hole for example I cut diagonal lines and a lengthways mid-line like the back of a letter and folded in on itself. Refer to the attached image to see the stereo cut-outs.
Step 6: Build a Box
I put the front, back and sides on a level surface and used wood glue to stick together.
I then placed a band clamp around and left for 24 hours.
Since there will be overlapped vinyl wrap the glue won't take a strong hold I just glued them to make it easier for screwing them together I used two screws per joint, near top and near bottom while the band clamp was still attached.
After I had finished with the 4 sides I then screwed the base to the bottom and left the lid until later.
Step 7: Stereo and Antenna
The stereo I used was a Kenwood BT30 model.
I have attached the ISO wiring as an image.
With car stereos you will have a port in which you would usually insert a plug which then adapts to standard car ports when you replace the stock radio.
Cut the wires just before the adapters the Yellow (BATTERY) and Red (Ignition/ACC) cables both had connectors on which I left.
You should be able to find a list of the different colour codes and what they do from a quick search on google.
I combined the Yellow and the Red cables by stripping the wires back about 20mm and twisting them around each other then soldering them, leave them at this length for now, will be cut when attached to switch.
I will continue with the other wires over next few steps.
If you have already cut a hole for the antenna in Step 3, then attach your antenna through this hole, if not you will have to drill a hole big enough to fit the antenna bolt through.
Once you have fitted the antenna insert the plug end into the back of the stereo.
Step 8: Speakers
Time to fit your speakers.
Place your speaker on the front of the panel like my poor 3d model shows and mark where the bolt holes should be with a permanent marker.
I used a drill bit to make holes and just drilled straight through the vinyl wrap.
Using the correct size bolts and nuts attach your speakers on the inside, I used some that I already had.
You will be able to see the bolts on the speaker in the video attached, this was taken before I ordered some grills and added the ports to the side.
If you're lucky your speakers will come with wires with terminal connections already attached if not, you'll have to crimp some connections on to both a positive wire and negative wire for each speaker.
BEFORE SOLDERING these wires together ensure you slide your heatshrink sleaving on then over the connection once the solder has cooled and heat the sleaving up. Nobody likes exposed wiring.
Take the positive wire for the left speaker (looking towards the speaker) and then solder this to the WHITE (FRONT LEFT +) cable from your stereo. This may be a different colour on yours so check your wiring guide for your stereo.
Take the negative wire for the left speaker (looking towards the speaker) and then solder this to the WHITE/BLACK (FRONT LEFT -) cable from your stereo - This will be white with black stripes. This may be a different colour on yours so check your wiring guide for your stereo.
Take the positive wire for the right speaker (looking towards the speaker) and then solder this to the GREY (FRONT RIGHT +) cable from your stereo. This may be a different colour on yours so check your wiring guide for your stereo.
Take the negative wire for the right speaker (looking towards the speaker) and then solder this to the GREY/BLACK (FRONT RIGHT -) cable from your stereo - This will be grey with black stripes.This may be a different colour on yours so check your wiring guide for your stereo.
Step 9: Battery
You may want to buy a premade Li-Ion battery and save a lot of hassle or.....
I originally bought 8 Li-Ion batteries making my pack a nominal 14.8V at 6000mAh but this was not enough capacity to get all the way through a 8 hour day at high volumes so bought another 4 and added another parallel run to get another 3000mAh.
The batteries used are 18650 (this is the size, they're a little fatter than an AA battery). I believe that they were bought from a reputable seller on eBay. The nominal voltage (the expected voltage) you get from a 18650 Li-Ion cell is 3.7V and usually have a capacity of 2950mA.
When browsing eBay or similar you'll see all the standard '10,000mah!!! ' or 'ULTRA HIGH CAPACITY' etc.
Avoid they're fake.
For those who do not know. When you position batteries [POSITIVE-NEGATIVE][POSITIVE - NEGATIVE]
this arrangement is called Series and when you position batteries like this the voltage will increase. Now if you were to arrange them like below in a Parallel layout the capacity increases.
Since my project runs with car/automobile parts I require a voltage of 12V - you will see on your car stereo specs what voltage it can accept.
When connecting Li-Ion batteries together the best option is to spot weld them with metal strips. Soldering them together is frowned upon as the time that the iron is in contact with the battery heats up the battery and damages them. I did not want to buy a spot welder as the cost of this project was rising fast. There are a few Instructables posts about making your own spot welder but I thought I'd try save a bit time. I spent a lot of time looking at different methods and found these kits from Vruzend. They also sell their kits on eBay which is where I bought mine.
Vruzend have guides on their website which I will not copy directly. I organised my battery in a 3P4S configuration which means 3 Parallel 4 Series with the parallel runs coming first .
Before assembling the battery using a normal 18650 charger like the ones meant for Vape users charge up each cell until your charger goes green or stops
I apologize for my 3D modelling skills, I just thought this would show the steps easier.
- Align all your cells the same way. Measure all voltages and then group cells in 3's with similar voltages, some of mine were 4.17, 4.18, 4.2 etc.
- I stuck the red caps to positive and blue to negative then pieced together as shown in (2).
~~~Test with a multimeter that the cell reads a voltage, do this on each step as it's a pain unscrewing those tiny nuts when you haven't placed one of the caps correctly (talking from experience)
- Put together the parallel blocks first, line 3 of the cells next to each all red caps on top all blue caps on bottom as shown in (3) use a book or piece of wood to squeeze caps level.
- Connect parallel blocks together in same arrangement as image (4).
- There should be some bus bars most are in a rectangle shape and there will be a few with rounded tabs on the end meant for soldering your connections on, use one of these on your negative side and place a normal one connecting the negatives on your first parallel block shown in image (5) You can attach the nuts to these bars as this section has no series link
- Just using the normal bus bars place on the bottom side on the first positive section as shown in image (6) for now just attach some nuts lightly as there will be another layer of bus bars making the Series connection
- Repeat step 6 but for the first negative section on the bottom side as shown in image (7).
- Turn your battery back top side up (the side with the longer bus bar on the negative section) and repeat what you have done for steps 6 and 7 but for the first positive section on the top again just screw nuts lightly. Image (8).
- Turn your battery bottom side up and undo the nuts you put on in steps 6 & 7, now place the connection/bus bars connecting the positive to the negative and tighten nuts properly. Fully recommend getting their 5.5mm nut driver, I struggled with a set of pliers. Refer to image (9).
- Turn your battery top side up and place your connection bars on the next negative section shown in image (10). Just tighten the nuts a little for now as series connections will be made on this once we have connected the opposite side of these cells.
- Turn battery bottom side up and connect the bus bars on the second positive section. Image (11).
- Turn battery top side up and connect the positive section from step 8 and the negative section from step 10, screw the nuts on tight now. Pattern shown in image (12)
- Turn battery bottom side up and connect the bus bars on the second negative section. Screw nuts lightly for now Image (13).
Turn battery top side up and as you did in step 5 attach one of the longer bus bars meant for soldering to the final positive section and one normal one also. Tighten the nuts on this one. Image (14).
Turn battery bottom side up and remove the nuts from steps 11 and 13 then attach bus bars connecting the 2nd positive to 2nd negative sections. Screw nuts tightly. Your battery will be around 14.8 V depending on how charged your cells were so be careful with not shorting any connections as it packs a punch.
A: Place the Negative probe of your multimeter (when in voltage mode) on top the top negative section (the first one you did) and the positive to the same cells but positive side (first section you did on bottom), you should get a reading somewhere between 3.7 and 4.2
B: Leaving the Negative probe of your multimeter in the same position place the positive probe on one of the parallel bus bars of the first positive section on the top, You should get a reading between 7.4 and 8.4V
C: Leaving the Negative probe of your multimeter in the same position place the positive probe on one of the parallel bus bars on the second positive section on the bottom of your battery and should get a reading between 11.1 and 12.6V.
D: Leaving the Negative probe of your multimeter in the same position place the positive probe on one of the parallel bus bars of the final positive section on the top, You should get a reading between 14.8 and 16.8V.
Using a good quality wire solder two black coloured wires on top the elongated bus bar on the Main negative section on the top of your battery, remember to put a little black coloured heatshrink sleeve on the wire before soldering and heatshrink after. (17)
Using a good quality wire solder two red coloured wires on top the elongated bus bar on the Main positive section on the top of your battery, remember to put a little red coloured heatshrink sleeve on the wire before soldering and heatshrink after (18)
Your BMS (Battery Management System) may differ from mine.
A: Take the wire you soldered in Step 17, (0V - Negative) and then solder to the 0V part of your BMS.
B: Turn your battery bottom side up and the first positive strip (if you put your multimeter on you should get a reading of somewhere between 3.7 and 4.2) remove a nut from the middle part as shown in image (19B) wrap two separate wires on the pole and screw nut back on, solder these to the pole.
C: Take one of the wires from previous step 19B and then cut to appropriate size and solder to the tab on BMS marked 4.2V. Electrical tape up the end of the other wire and label 4.2v (19C).
D: As shown in image (19D) attach and solder two wires as you did in step 19B to the positive section, where you should get a reading between 7.4V and 8.4V. The image only shows one wire but do two and like the previous step cut and solder one of these wires to the section marked 8.4V on the BMS and then label and tape up the other wire for later.
E: As shown in image (19E) attach and solder two wires as you did in steps 19B and 19D to the positive section, where you should get a reading between 11.1V and 12.6V. cut and solder one of these wires to the section marked 12.6V on the BMS and then label and tape up the other wire for later.
F: Take one of the positive wires from Step 18 and solder to the 16.8V (max) tab on your BMS, label and tape the other wire which should measure between 14.8 and 16.8V.
Step 10: DIN DIN DIN
As I chose to charge my radio with my imax b6 charger I found that the small JST-XH connections were a bit small and flimsy so I decided to look into other options for which type of connector to use.
I still wanted something small and that had 5 pins (0V, 4.2V, 8.4V, 12.6V and 16.8V) for the balancing I finally decided on using DIN I had used these connections with Midi keyboards in the past and found the connection was easy enough to use.
Screw a terminal strip with 5 slots on the inside of your box, this makes removing the battery if needed easier than having the battery connected directly to the DIN port.
Take the extra balance wires that were soldered while doing the battery (should still have labels on) and place each one into a a slot on a terminal strip and tighten.
Now we need to solder a wire to each of the pins on the female DIN port, going from left to right looking direct at the pins you should go from 0V to 16.8V. Remember to place heat shrink tubing on each wire the seal the pins up. I colour coded the wires again so I'd match up with the correct ones on the terminal block.
Take a 4S JST balance wire (the type of connection needed to plug into the Imax B6 and cut the female adapter off. Take the DIN cable and also cut one adapter off. The length of your cable is up to you, I kept mine short. These wires will then be soldered together remembering to feed all wires through a larger heat shrink tubing before and also placing heat shrink on each wire before soldering.
Step 11: Rocker Switch and DC Port
Rather than removing connection wires from the battery each time I wanted to charge it I thought it would be easier to feed everything through a switch.
3 Position switch.
Position 1 (I) would connect the D.C port on the side to the battery. (For charging)
Position 2 (O) would not connect the battery to anything.
Position 3 (II) would connect the battery to the Stereo switch and USB charging switch (which will install next step).
- Place the rocker switch in the side panel cut out.
- Using hot glue secure the switch
- Take the main outputs from the B.M.S that was connected to the battery using a crimping tool crimp an insulated female connection on the end of both the Positive (RED) and Negative (BLACK).
- Push these connections on to Pins 3 & 4 of the rocker switch.
- Solder a red wire to the positive pin of your dc port and a black to the negative pin use thicker wires for these connections if you have.
- Slide some heat shrink on to both of these wires and seal pins.
- Feed wires through DC port hole cut when you did the side panel
- Hot glue the port in place.
- Now take the other end of these wires and again add female crimp connections on to each.
- Push these connections on to Pins 1 & 2 (this means when the top end of button is pressed in the DC port will be connected to the battery (through the BMS)
- Take another length of red wire and black wire (thicker wires) and again strip back the end of each and connect female crimp connections.
- Leave these two disconnected for now as these will be connected to some other things before the rocker switch and may be easier to work with them disconnected.
Step 12: USB Module and Switches
First the switches.
On the front panel where you cut holes for the switches stick your rockers in here, yours may have a nut to tighten or you may have to glue them.
Take the positive cable you made during the previous rocker switch installation (the one left unattached) and solder two separate wires to the end that was not crimped. Like a Y connection. (REMEMBERING TO HEATSHRINK).
There will be three pins on each rocker, yours may be labelled or have markings on. Usually the GROUND connection is a different colour pin and usually the middle pin is the power and the last pin connected to the actual thing it will switch.
Take one of the wires from the Y connection you made earlier and strip a little bit and then crimp a female terminal connection on the end so that it can be attached to one of the rockers (choose which one you want for USB and which you want for POWER). I chose the RED backlit rocker for power. Connect this cable to your power switch.
Now repeat this process with the other positive cable from the Y connection and connect to the rocker switch which will be used to switch the USB port. Still leave the main end that is crimped unconnected to the DPDT rocker switch.
The Negative BLACK cable that you also made when installing the DPDT switch should now be soldered to 4 wires, keep them with length as can trim down to correct size afterwards, again make sure that you slide the heatshrink over the main cable before soldering.
- Solder to the BLACK/GROUND/NEGATIVE connection from your Stereo harness
- Solder to or connect (if you have screw terminals on your module) to the Negative/ground connection on your USB module/port.
I decided that USB ports would be a good addition to my stereo since there's always someone at work who has forgotten to charge their phone or charging a vape pen etc.
I looked on eBay for a 12v dual USB module and bought one of the first ones I saw. This module had a 12v input but the output was not something that could go on the front panel of the radio, so I also bought an extender which was panel mounted.
A car 12v USB socket would be a better purchase since you could unscrew the back and then solder directly on to the connections using the front on the panel.
Step 13: Cable Tidying
There will be left over wires from the back of your stereo.
From the Kenwood one I used.
BROWN // MUTE - Unused
LIGHT BLUE/YELLOW // STEERING REMOTE CONTROL - Unused
The following will be part of the ISO Connector
YELLOW // POWER - Combined with RED and connected to the power switch rocker on front of box
BLUE/WHITE // POWER CONTROL - Unused
RED // IGNITION ACC - Combined with YELLOW and connected to the power switch rocker on front of box
BLACK // EARTH (GROUND) - Combined with the ground connections from the power rocker switch, the USB rocker switch and the USB module then connected to the DPDT rocker on side of box.
PURPLE // Rear right (+) -Unused
PURPLE/BLACK // Rear right (-) - Unused
GREY // Front right (+) - Connected to right speaker positive
GREY/BLACK // Front right (-) - Connected to right speaker negative
WHITE // Front left (+) - Connected to left speaker positive
WHITE/BLACK / Front left (-) - Connected to left speaker negative
GREEN // Rear left (+) - Unused
GREEN/BLACK // Rear left (-) - Unused
Confirm that your wiring guide is similar and then cut the unused cables shorter and slip a little heatshrink and close them off - I cable tied mine together.
Step 14: Power on Time
- Turn the two front rocker switches to the off position and also the side rocker switch to Position 0 (flat, not in at top or bottom).
- Take the Negative/Ground (BLACK) wire from the BMS attached to your battery (if you built your own, otherwise just take the negative output from a premade one) and slide the crimped connection on to the side DPDT rocker switch this should be one of the middle pins, refer to STEP 11.
- Take the Positive (RED) wire from the BMS attached to your battery (if you built your own, otherwise just take the negative output from a premade one) and slide the crimped connection on to the side DPDT rocker switch this should be one of the middle pins, refer to STEP 11.
- Now turn the side rocker to Position 2, so that the battery is now connected to the two front rocker switches.
- Switch the Stereo power rocker to ON, this should light up if you bought backlit ones and the Stereo should now switch itself on and go in to Standby mode.
- Take your stereo out of standby and find a song to pump through your speakers via FM radio / Bluetooth / Aux or whatever your stereo lets you source from.
- Now time to test USB sockets if you installed, switch the USB rocker switch to on and find a phone charger or similar to plug into the ports.