Friday, 2 February 2018

Reinforced Retaining Wall

Reinforced Retaining Wall - Intro 


This a a quick post to show some pictures of a reinforced retaining wall, along with a little non technical description, along the way.

A retaining wall is generally a wall you would build to avoid having a steep slope, or where you want to have a change in ground levels without a slope. Opting for a step instead. Retaining walls can be just a few feet high, or many meters.

Reinforced Retaining Wall - Basic Concept


If you were to stand a domino on its end, it could be easily pushed over. If however, you were to super glue the domino to a heavy table, it would a a lot harder to push over. Provided the glue were strong enough you would have to tip the table over to get the domino to topple.

In the same sense a concrete wall, can be easily pushed over by heavy soil pushing against it from one side, so we must attached the concrete wall to something heavy to stop it moving.


So we anchor the concrete block wall to a concrete slab. This is done by setting steel bars in the concrete footing, as shown above. The soil will try to push the wall, but with the weight of footing and the soil resting on top of the footing it will not move (providing the soil under the footing is not too squishy - a geotechnical investigation would determine this).

It is also important to let the ground water drain out from behind the wall. Gaps or pipes must be included to allow this.


Reinforced Retaining Wall - Case Study


In the below picture you can see the footing for the retaining wall has been cast, and the steel bars (rebar) are left poking up, ready for the wall to be attached to.



Next up the block wall is built up around the rebar. The block are hollow as they will be filled with concrete at a later date. Another option would be to build a wooden mould (shuttering) around the rebar and pour concrete in to the mould to make  wall.


As the wall is built horizontal bars are added, these are tied with thin wire to the vertical bars to keep them in place.


You can see here how the wall is built to one side of the footing. This helps keep the wall stable, as it will be loaded from (in this picture) the left hand side.


You can see more clearly here the thin wire sued to hold the bars in place prior to pouring the concrete.


On a very long wall such as this one you will need to have expansion gaps, these are breaks in the wall filled with squashy (compressible) material that allow the wall the  expand and shrink when it get hotter and colder.

Reinforced Retaining Wall - A Simple DIY Design

This retaining wall as pictured was likley designed by an engineer. And it is next to a railway so it is a very high quality, probably over specified retaining wall. 

For DIY purposes retaining walls can be built without reinforcement, from normal concrete blocks sometimes without any footings. But drainage is still very important. 

A method I have tried is a a thin strip footing topped with a concrete block wall. The blocks are laid on there side, and can be sloped gently back towards higher ground. If you do slope the wall back fill as you go. Gently pack the soil behind the wall. Every 4 or 5 block insert a length of 50mm drainage pipe between the blocks to allow of drainage. 

Wednesday, 17 January 2018

Shimano V Brake Pads / Shoes / Blocks Compared

Shimano V Brake Pads / Shoes / Blocks Compared - Intro


Shimano make  V Brake Pads / Shoes / Blocks with a number of different compounds. This compound can be softer of harder for example to suite different rim types. Each Pad / Shoe / Block, has its own model number so you can find out which you prefer.

Shimano V Brake Pads / Shoes / Blocks Compared - Threaded 

The Below Pads have a Threaded Fitting

M70T3

70mm - Threaded Type - Performs especially well in wet conditions and may pass DIN standards. Gives off less noise, but the pad is heavier, faster rim wear and tends to fade.

M70T4 & M70W


70mm  - Threaded Type - Only for side wall machined rims. Performs especially well in wet conditions and may pass DIN standard. Tend to be low noise, low rim wear and fade.

S70T & S65T


60mm or 70mm - Performs well in dry conditions and tends to be low noise. Wears in muddy conditions

Shimano V Brake Pads / Shoes / Blocks Compared  - Un-Threaded


The below pads have an UN-Threaded Fitting

M70T2 


70mm - Performs especially well in wet conditions and may pass DIN standards. Gives off less noise, but the pad is heavier, faster rim wear and tends to fade.

M65T & M55T


65mm & 55mm - Un-Threaded - Performs especially well in wet conditions and may pass DIN standards. Faster rim wear and tends to fade.

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Tuesday, 9 January 2018

Top 5 Class D Amplifier Boards

Top 5 Class D Amplifier Boards - Intro


This page title should also have "low cost" added. All of the below boards cost less than £8 / $10, so make for a very low cost project, just be aware you will need to power these boards, and for the louder options below this can cost 2 or 3 times the cost of the board itself.

The below descriptions are boards I have owned and tried. All chips (8403, 8610 etc.) will behave differently depending on the boards used. For example if a specification says 24V, but you board has 22v capacitors, then you will not be able to run the max voltage.

Also just because a board has more capacitors and knobs on it does not mean the chip will be louder or better. The best results I find come from the most simple boards.

Top 5 Class D Amplifier Boards - 1 - PAM8403


Cost: £1 / $2
Voltage: 2.5V to 5V
Output: 2 x 3W

The top slot goes to the the PAM8403, this is the size of a postage stamp, and you can run it from a USB power supply, or 3 x AA batteries or a single lithium cell.

Its power is rated at 3W, but it is incredibly efficient, producing a room full of sound, when using 4ohm speakers.

My favorite class d amplifier, fiddly but fiesty!


If you have an old hi-fi speaker of any sort hanging around you could convert it to an active speaker, for perhaps just £2 / $4.

I have placed this board at number 1, because it is:


  • A versatile low cost amplifier
  • Very easy to power
  • Very very efficient
  • Good quality sound at all volumes
  • A lot of volume when considering low cost of board and power supply. 
Note: You can not run 1 speaker from this amplifier, both of the outputs have to be used to avoid damage to the chip. I have run a tweeter from left and woofer from right to get around this which is OK.

Top 5 Class D Amplifier Boards - 2 - PAM8610



Cost: £2 / $4
Voltage: 8V to 15V
Output: 2 x 15W


Second place, but only just. 

The PAM8610 is the logical step up from the PAM8403, it requires a higher voltage to work, and the low volume sound quality is not overly good, but it produces a very high volume for such a small amplifier. Get the basic board if you are buying with no heatsink or volume control, you do not need one. 



These is s light deterioration in sound quality at low volumes which some might find annoying. This can be well powered from 8 x AA batteries, or a cheap 12V wall socket transformer.  If you are running this amplifier from a SLA or Car Battery be a bit careful, because these sometime creep over 15V with some chargers. 


Top 5 Class D Amplifier Boards - 3 - TPA3116 


Cost: £5 / $10
Voltage: 8V to 24V
Output: 2 x 50W (Official) 2 x 15W (Real World)


This amplifier is comparable in output to the PAM8610, the sound is a lot cleaner to. But this is offset by the difficultly in proving 24V to power it adequately, it will work from 8V but you will have very low power levels until you reach 18V upwards.

I tried a complex 3 channel board, perhaps give a simple one a go.


That being said this is a versatile amplifier that will run on a very wide voltage range. The sound is crisp and clear at all volume levels, although high volume sound will be distorted if you are using an under powered supply. 

I used a 3 channel variant of this board which is so say 50 + 50 +100W, but is no where near this loud. Perhaps the board which uses NE5532 pre amplifiers. And the gain is fairly low.

Top 5 Class D Amplifier Boards - 4 - TDA2030

Cost: £3 / $6
Voltage: 8V to 16V - Will go higher on some boards. 
Output: 2 x 50W (Official) 2 x 15W (Real World)

This is actually a AB class amplifier, which is fairly inefficient. However it is small and cheap and reasonably easy to power. The sound is far richer than any of the above amplifiers, with a warm sound many will fine pleasant. 

It is not great for running from AA batteries but will run well from an SLA battery. It cannot be run from AA batteries as the power requirement is to high. 


Top 5 Class D Amplifier Boards - 5 - OEP3W or XTP8871

Cost: £1 / $2
Voltage: 2.5V to 5V 
Output: 3W Mono / 5 W Mono

I couldn't quite decide between these two they are both excellent boards that they can be powered from a USB port, requiring only 1A of power. Mono is easily achieved my mash together the positive and negative input wire. You then one have to find one speaker to use these amps, which lowers the costs still further. 



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TPA3116 Amplifier - Power Supply

TPA3116 Amplifier - Power Supply - Intro


I am not an electrical engineer. Perhaps this is why I have tried this amplifier with 5 different power supply options. Including 12V, 15V, 20V, 24V  all have worked to some extent. Which shows this amp although needing a hefty power supply to produce loud music will, produce varying volumes from all different types of supply provided they are within spec voltages of 6V to 24V.

System: This is based on the 2 chip 2.1 board with NE5335 pre-amps. My input source was an Iphone 6, connected via a good old fashioned aux cable, via the 3.5mm headphone socket.

TPA3116 Amplifier - Power Supply - 12V 2A Wall Socket Power Supply

This worked OK, but the volume was very low. The sound was perfectly clean, noy problems really but very underwhelming volume.

12V 2A - Cheap and Works to an Extent

TPA3116 Amplifier - Power Supply - 12V SLA


I have tried this amplifier on 2 types of lithium batty which are design to replace SLAs, the shido LTX9-BS and the EV Power 7ah 12v LiFePo4 Pack.

The Shido LTX9-BS is the closest match to a true SLA as it gives out many many amps peak current. Powered by this SLA equivalent the TPA3116 gives out clean rich sound at a fairly low volume. Perfectly adequate for a lounge listening, or for speaker computers for example, but certainly not party loud.


SLA or Alternative OK for Low Volume


TPA3116 Amplifier - Power Supply - 12V to 24V Transformer from SLA


I have also tried a "Fulree" Step-Up converter, rated at 3A this gives more gain for lower input volume, but I suspect the 3A max current is not high enough to support the TPA3116 at high volumes.

I have tried this 12V - 24V Step-Up converter powered from the above Shido battery and also powered from a 20V 90W (4.5A) IBM Thinkpad Power Supply.

The TPA3116 will cut out (I Think) if it is not getting enough current. I have arrived at this conclusion because whilst using the 12V - 24V Step-Up converter, the cut out occured at a lower volume when running from 12V than it did at 20V.

The 12V - 24V Step-Up converter supplies more current if it has to make up for smaller differences in voltage, so a lower volume cut out when supplying less amps would suggest a current cut out are caused by low current. The step up converter does com,e in a 10A variant which would be a better choice.

10A Variant preferable to 3A Version

TPA3116 Amplifier - Power Supply - 20V 4.5A Laptop Power Brick


At 20V this amplifier really starts to shine. The input source (Iphone) can be turned up to full volume with very little distortion. You also begin to feel the bass rather then just hear it. The sound is clean and crisp, and there is little or no hiss.

The good news about this power supply is that you probably already have one! Most laptop bricks run 19V or 20V, and although some may only kick out 2A this will be fine for a board with a single TPA3116 chip.

If you do not have one then I would suggest search for a "Thinkpad T60" power adaptor, they are 20V 4.5A and sell for £6 / $10 including shipping.

Excellent Sound - Feel the Bass - Excellent Value

TPA3116 Amplifier - Power Supply - 24V 6A Power Brick


I had to max this thing out, so I went for the 24V 6A "Minger" power brick that is available on Ebay and Amazon. After all I had tried nearly every other power source! So why not one more to make a good blog post.

24V power brick are quite expensive compared to 20V one, I had to pay £16 / $25 for this supply.


For Maximum Power and Higher Low Input Gain. 
ESDM Report

Tuesday, 2 January 2018

SPL10M.1 Review & Observations

SPL10M.1 Review & Observations - Intro


The cheapest 10" driver on ebay lead me to the SPL10M.1, this is a large speaker and is certainly heavy but is not a sub woofer. It is just a very large mid-bass driver. It is very well built, I paid under £20 for this peaker, and it is excellent value. But it has a weird spec!



I am not sure why it is so large, but for a low power application as I intend using a TP3116D2 amplifier I assumed it would be OK.



SPL10M.1 Review & Observations - Out of the Box


First things is that it is heavy. Second thing is that is built OK. The spring terminals have a reasonably high quality feel, and the materials look well finished. The cone is paper, rather then fancy new fangled material, but this is fine as I have used some very good speakers that have paper cones in the past. The stainless steel thing in middle of the speaker (phase plug?) is a high quality feature, at least aesthetically.



The box itself is a bit disappointing with little protection offered to the speaker. However at the price I bought this I doubt they wanted to spend extra ££ on wrapping!

SPL10M.1 Review & Observations - Performance

I have powered this up to around 50W with low frequency sound (it is not design for this) but performs well. I will attempt to describe the sound, but I am pleased with the purchase.


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TPA3116D2 2.1 - Observations

2.1 Channel TPA3116D2 - Observations - Intro


I have recently purchased a TPA3116D2 from ebay, it is a 2.1 channel variant. So it uses two chips one for stereo and the other for a subwoofer.

Official specs put a single TPA3116D2 amplifier at 100w or 2 x 50w (depending on configuration).

This is wildly optimistic as a power rating, at 20V this board will make about 30W, at 24v it swill draw around 40W. Remember this is for Two TPA3116 chips, so if you have a single chip variant you can expect half the wattage!

The sound is still very full and loud, so this amp is no doubt efficient but why even the official specs talk of 50W per channel I do not know.

Do not be swayed for your choice, this amp does give good sound and these days even a 3W per channel amp such as the PAM8403, can sound good.

2.1 Channel TPA3116D2 - My Board (From Ebay)


2.1 Channel TPA3116D2 - Observations - Power Supply Choice

For in depth view of TPA3116 power supplies

The 2.1 Channel TPA3116D2 apparently will produce 100w output at 21v in to a 4ohm speaker. This would point at a power supply being rated at 5A for a single chip. However you will not need a 5A  power supply because the specs for this amplifier are inaccurate. A 2A power supply for a single chip amp and a 4A supply for a dual chip will likley suffice.

If you are  running the 2.1 Channel TPA3116D2  at lower voltages I have noticed the following:

12V / 2A - A wall adaptor used for power provided clean sound at max volume. The max volume was reasonably low however. This was tested using 6 ohm speakers.

14V / 7A - Using a lithium 12v battery pack with a rated output of 7A (fresh off charge = 14v). This provided more volume but lots of distortion much above 60% volume. Thus used 4ohm speakers for stereo and a large 10" 4 ohm woofer for sub.

Note - If you are planning on using 2 x SLA batteries at 12v a piece be careful. Although these are labelled at 12v, often they will hold 15v when fresh off the charger. So it is possible to accidentally supply your TPA3116D2  with 30v which would not be a good idea.


Choose Voltage Carefully - 22V to 24V to avoid disappointment


2.1 Channel TPA3116D2 - Observations - Output

When running a a 4ohm load at maximum volume, with a 20V 4A supply this amplifier draws 30W. Does this mean that this amp is really 30W RMS? I measured this with a wall socket watt meter.

I was expecting some serious output from this amp. I have used 20W (2x10 @8ohm/12v) PAM8610 which  runs on AA batteries, and running this board at a similar voltage, the PAM8610 wins hands down. The PAM8610 is I would suggest a much more efficient chip (?) although my electrical knowledge  is limited.

To power this amplifier to a level where it begins to shine you will need a 20v supply, have a look at some of your old laptop adaptors! They may be perfect. I do not think you will need a very high amperage adaptor. 4A should be plenty. 

2.1 Channel TPA3116D2 - Observations - My Build

I was expecting a great deal of power from this amp, so I built a very large speaker. I used:


  • 2 x 8 Ohm Tweeters*
  • 2 x 8 Ohm Mid Range* (30W rating)
  • 1 x 4 Ohm Woofer (SPL10m.1) (75W rating)
*These are linked in parallel, to give 4 Ohm load. The tweeters have a high pass crossover in form of capacitor. 

I built these in to a 15mm plywood box, which stands around 60cm tall, and requires handles to lift. Most of the weight comes from the wood and and the SPL10.1 which weighs a few kilos on its own! The midrange speaker has their own enclosure inside, to prevent the woofer from influencing them.

I used a pice of plate steel to to mount the amplifier board, using just the potentiometer bolts to secure it. I then cut an extra hole for a plate with RCA connectors. Lastly after first experiments with batteries I installed a IBM think pad power supply which give 20V 4A Supply.

I used a piece of fabric we had lying about to cover the front of the speaker, as I want a neutral "furniture" type look for the thing.

My most pleasing design choice was the use of a piece of 100mm waste pipe for a bass port, this runs side to side at the top of the enclosure, the opening can be used for hand holds for carrying the the speaker.

2.1 Channel TPA3116D2 - Observations - Sound and Performance

Powered at 20V with 4 ohm loads the sound is fine for loud personal listening. The range of sound is really great, the low frequency oomph being the most pleasing feature. The bass will travel throughout the entire house and vibrates things of shelves nearby. 

The amplifier is not very loud when listening to bass free music, it reserves 50% of it power just for bass, so listening to say vocal rich music is a little underwhelming, although the sound is very crisp and clear at all volumes. 

The sound quality I would rate as excellent, however a bit more quantity would be nice! Especially as the Texas Instruments specs are nearly 600% out. 

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Tuesday, 5 December 2017

EMWC - Reverse Osmosis - 5 Stage - Review & Fitting Tips

EMWC - Reverse Osmosis - 5 Stage - Review - Intro


First off if you are buying this to treat tap water in the UK don't bother. Tap water in the UK is the most highly regulated in the world, in terms of quality. Depending on where you live you may be lucky enough to get mineral water out of you tap for free!

Residents of Portsmouth for example get beautiful calcium rich chalk aquifer water out of their taps. And the Drinking Water Inspectorate place strict limits on any nasties full stop. Do not bother treating mains tap water.

If you however use borehole water that is contaminated with heavy metals, pesticides or other then please read on . . . .

Takes up Most of Room Under Sink - Not a lot of room for Washing Up Liquid


EMWC - Reverse Osmosis - 5 Stage - Review - Cost


The East Midlands Water Company sells well priced reverse osmosis units, at around the £150 mark at the time of buying. This is pretty cheap considering how complicated the unit is. However, just like buying a cheap printer, you could expect to make up for it with the cost of the cartridges. The 5 filters in the units at present are around £60 to replace, although you can order extra for not much money.

EMWC - Reverse Osmosis - 5 Stage - Review - Quality


This worries me. I am not saying that the RO unit does not function, but the connections between filters are numerous and the the fitting are small and do not inspire confidence.

The unit operates at mains pressure! So small screw fit plastic connectors make be worry a bit. If one of these "popped off" there would be £1000s of damage done in just a few hours. Other higher cost system feature much more robust connectors and less of them.

Plastic Fittings do not Feel Very Sturdy


Like I say I am sure it is fit for purpose, but this is a mains pressure system, and as such could be conceived as a bit flimsy.

The instructions that come with the kit are OK, but a bit more details wouldn't go amiss. Also I did not have enough inserts to put in all the pipe ends. Which was a bit annoying, how much does an insert cost 1p? And I was short. The fitting for the top of the pressure vessel will not seal with PTFE tape, so get a role of that prior to fitting. Again they could include roll of this (50p), you need it for fitting.


EMWC - Reverse Osmosis - 5 Stage - Review - Fitting Tips


Fitting is fairly simple. But any mistakes will lead to much damage from leakage so this ups the stakes a bit, it is not an enjoyable process knowing the risks are so high. Especially considering the flimsy nature of the connectors. For fitting you will need:


  • Drill with c.12mm drill bit - To make hole in sink for tap.
  • File Possibly - To enlarge hole in sink.
  • Smaller drill bit - for fitting waste pipe
  • Some silicone to seal waste pipe, if not using kit (optional extra)
  • Screws and screwdriver for mounting inside cupboard
  • Sharp knife and chopping board to cut pipes to length
  • Adjustable spanner for tap fitting.
  • PTFE Tape to seal tank threads
PTFE Around Tank Thread


It took me around 3 hours. Although the last hour I was also cooking tea at the same time. 

EMWC - Reverse Osmosis - 5 Stage - Review - Taste


The water tastes pretty flat, this is to be expected as you are pretty much drinking distilled water. Mineral filters are available to the put the minerals back in before you drink it. I have not done any analysis on the water to test how effective the treatment is. 

Lots of Tubes!


EMWC - Reverse Osmosis - 5 Stage - Review - Conclusions


This is certainly is as very cheap option for those wishing to treat water to a high state of purity, however the fittings do not inspire confidence. 


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