sexta-feira, 8 de abril de 2016

An exercise on DIY circuit boards

Still hand-made, still without etching, a lot more tidy...

In this case a voltage regulator for a small solar panel

quinta-feira, 7 de abril de 2016

A reflection on silent crack propagation...

A close-up inspection of Fulô's standing rigging tensioners revealed this:

A close call...

quarta-feira, 22 de julho de 2015

A FEM based comparison study regarding different steel sections with similar specific weights

A college degree stays a long way from providing the empyrical knowledge a designer needs in mundane, everyday work. 

Fast and safe simple designs are often needed for things such as simple levers, hoists and similar devices and I find myself often in need of knowing how different sections, with close specific weights, behave in similar load conditions.

As such, today I decided to establish and share a reference comparison  between similarly weighted steel beams with very different sections loaded in identic scenarios.

The results are as follows, using Autodesk Inventor Professional 2016's Stress Analysis:

Sections properties
Mesh settings

Fixed support at one end, 1000N vertical load at the other (evenly applied across the sections faces)

Von Mises stress

Load scenario animation (Von Mises Stress propagation)

Fixed support at one end, 1000N horizontal  load at the other (evenly applied across the sections faces)
Von Mises stress

Load scenario animation

Fixed support at one end, 100Nm torsional moment  load at the other (evenly applied across the end faces)

Von Mises stress

Load scenario animation



quinta-feira, 7 de maio de 2015

Fulô waking up on a spring morning

The only (as far as I'm aware) Piver Nugget 24 in Portugal waking at its mooring yesterday.

segunda-feira, 6 de abril de 2015

Mais uma subida do Tejo, de Alhandra a Valada

Desta feita na ressaca de longas semanas em terra por motivos estranhos à Vela, mas tanto ou mais pesados que ela...

Eu e o Neil a bordo do Fulô, o Elebore, o Já Agora, o Sheerazade e, mais tarde, o Falua (3) largaram d'Alhandra rumo a Valada para passar a Páscoa.

A prometida frota da ANC faltou, e nem sei se fez lá falta, tal era a paz assim:

A motor para os dois lados porque o vento não era grande espingarda, mas foi melhor, muito melhor, do que ter ficado em terra...

Aproveitei também para actualizar a minha contribuição para a navegação segura no Rio, já que outras, oficiais e gratuitas, como pertencem ao pagador de impostos e taxas, teimam em não haver:
O Rio continua sujo, assoreado, mal gerido e a piorar...enfim...

Rio Tejo- Ajudas Não Oficiais à Navegação

sexta-feira, 20 de março de 2015

DIY buffered effects loop/ AB box for guitar

A bit of a side project:


To build a simple (series) effects loop to add/remove noisy or otherwise malicious components (i.e. crapy bypass pedals) out of the signal chain when not needed.

The solution:

To add the simplest an purest sounding of all buffers to a simple 3PDT based switcher.

Materials needed:

1un. enclosure
4un. jack sockets
1un. 9V battery snap
1un. JFET
1un. 1Mohm resistor
1un. 3k3 to 10k resistor
2un. quality caps (anywhere from .22uF- Higher values means lower frequencies pass. I hear no difference from .47uF onward...)
2un. LEDs
2un. 390ohm resistors
1un. 3PDT stomp switch
1un. SPST toogle switch

Principle of operation:

1- The signal arrives from the guitar at the input jack;
2- It then enters the FET buffer which provides a high impedance input and a unity gain output signal. Great for driving whatever comes next (be it long cables or lots of true bypass effects).
3- From there it goes into the center of the 3PDT where it gets sent either to the OUTPUT or to the SEND jack
4- If sent to the SEND ith thet travel through whichever is connected to the SEND-RETURN and it is thrown into tht output. Simple.

5- The remaining pole of the 3PDT is used to provide a visible status indication (via one of the LEDs).

6- The toggle switch is used to turn the unit on/off.

The unit can be used as a AB box if the instrument is connected to the INPUT and oune output is pulled from the OUPUT and another from the SEND

The assembly results in a super silent unit that draws very little power and does not (at least to my ears) alter the signal in an audible fashion.

Have fun!!!

domingo, 22 de fevereiro de 2015

The Nugget- my first self designed stompbox

The most used effect in my gear, beside reverb, is a mild overdrive or clean boost.

I've built a few varations on EHX's LPB1 but, honestly, feel a bit ashamed of myself for having to copy such simple circuit and not forcing myself to learn enough about circuit design to conceive my own customized yet functional boost pedal.

So today the quest begins and this post will be the diary of the process. Lets see what happens.

1- REQUIREMENTS (22 Feb 2015)
     . High impedance FET input;
     . Dual switchable outputs (A/B) box style;
     . Switchable effects loop;
     . Active tone control;
     . Drive and/or fuzz circuit;
     . Optical output level regulation,
     . Switchable compressor.

So here we go! Keep in touch...

DIY wooden volume pedal

Celebrating the return to (more) frequent posts:

The (still passive) Volume Pedal!

Hopefully this serves as inspiration to anyone seeking a solution to build a simple, sturdy and fully functional expression pedal on the cheap

quinta-feira, 26 de junho de 2014

À bolina, rio acima (beating, upriver)

My pride and joy sailing in Alhandra, Portugal, in June 14th.

50 years after her construction, this Piver Nugget still rocks...

quarta-feira, 25 de junho de 2014

"The Buffer"

The unity gain amplifier, aka, “The Buffer”

1-      PROBLEMS:
a.       To have an extra output from my guitar so I can feed a low impedance input without loading the pickups, or keep my favourite tuner (which is a little noise box) in the signal chain.
b.      For the input of the chosen circuit to present a high impedance to the guitar;
c.       To be noise free and lean on power consumption;
d.      Easy to build with a minimalist parts count and featuring easy to obtain components;
e.   Suitable for point-to-point wiring (no PCBs or Veroboard)
f.      Not to modify the signal in an audible manner- No metaphysics here. If I can’t hear a difference, than there’s no difference.

2-      SOLUTION: A single stage FET unity gain amplifier, or a buffer as it is also known, with two parallel outputs:

Some theory on the subject here.

Here are the simulated signal comparisons:

A little signal attenuation (around -2dB @ 1kHz into a 10k load), as expected, but in practical terms nothing to worry about. I’ve implemented the circuit with 220nF caps both at the input and output. If you can hear a loss in bass response (I can’t) please do increase the value of the output capacitor. A 1uF cap will result in a slightly better bass response:

 You can obviously go for higher values but be prepared to pay extra for film capacitors of high capacitance.

Drawing only 0.7mA of current, a standard alkaline 9V block should be good for more than 150 hours of continuous use (assuming a lowball battery capacity of around 100mAh):

Parts list (circuit only):

1x N-channel JFET (I’ve used 2N3819 devices. 2N5457 and MPF102 should also work fine)
2x 220nF polypropylene "orange drop" film capacitors
1x 1.5MΩ 1/4W resistor
1x 3,3kΩ 1/4W resistor

Have fun!

terça-feira, 24 de junho de 2014

Rota Alhandra- Valada

Para quem quiser navegar rio Tejo acima até Valada aqui ficam as rotas seguras:

Para dispositivos Android (utilização com o Google Maps): Rota Alhandra-Valada KML

Para outros GPS: Rota Alhandra-Valada GPX


-A rota nos ficheiros foi traçada em 03 de Abril de 2015.
-Pode ser seguida por embarcações com até 3m de calado SE PLANEAREM A VIAGEM PARA CHEGAR A VALADA COM MAIS DE ¾ DE MARÉ CHEIA! À baixa mar na entrada de Valada (que é a zona mais crítica do percurso) apenas é segura para embarcações com um máximo de 1.5m de calado.
-Atenção às artes de pesca mal sinalizadas.
-Aconselha-se uma visita às RIO TEJO-AJUDAS NÃO OFICIAIS À NAVEGAÇÃO para observações adicionais.
-Estas rotas e recomendações são fruto do melhor do meu conhecimento e boa vontade e a sua utilização não dispensa o responsável pela embarcação de se munir e usar dos melhores conhecimentos de navegação, marinharia e bom-senso que lhe são exigíveis. Não me responsabilizo por acidentes, incidentes, aborrecimentos, ferimentos e outras chatices que possam ocorrer durante a utilização destas rotas.


For those who want to sail the river Tejo up to Valada here are the safe routes

For Android devices (use with Google Maps):Alhandra-Valada Route KML

For other GPSs: Alhandra-Valada Route GPX

-The route available in both files has been plotted in the 3rdJune2015.
-It can be safely followed by boats with drafts up to 3m IF THE TRIP HAS BEEN PLANNED TO ARRIVE IN VALADA LATER THAN ¾ OF HIGH WATER! At low tide in Valada’s entrance (which is the most critical section of the trip in what regards depth) the route is only safe for boats up to 1.5m drafts.
-Keep an eye out for poorly signalled traditional fishing apparatus.
-A visit to RIOTEJO-AJUDAS NÃO OFICIAIS À NAVEGAÇÃO is recommended for additional remarks.

-These routes and recommendations are provided at the best of my good-will and knowledge and their use does not free the skipper from gathering and using the best knowledge in navigation, seamanship and good-sense that he’s required to . I’ll not be held accountable for accidents, incidents, hassles, injuries and other annoyances that may occur while using these routes.

Have fun!

sexta-feira, 28 de março de 2014

quarta-feira, 26 de março de 2014

Fixing a BOSS FW3 wah pedal

Just the other day I found a BOSS FW3 wah wah on an auction site and got it for 40€. Although the previous owner stated it was in “mint condition” it was somewhat far from it. The slider pot (yes, this wah has a slider pot instead of a rotary one) had been messed with, removed and placed back again with hot melt glue. Fortunately is it working fine and I’ll worry about it when the need comes. Some of the screws holding the base plate were also missing and the pedal was soaked in oil , grease an fuzz…

The pedal was in good working order though, the seller even threw in a brand new Duracell 9V block, and the only real problem was what led me to write this post:

-          An annoying malfunction with the indicator LED was making it unable to keep lit when the effect was engaged. Instead it flickered or remained off…

This really upset me since the indicator is in my opinion a major feature on a pedal that more established brands (when it comes to wah wah pedals) incomprehensibly opt to rule out of their designs… The BOSS FW3 is also built like a castle and, even if it didn’t work at all, 40€ would be a fair price for the case alone as a DIY start point…The wah circuit was working fine though…

Anyway, I set myself to give the thing an overhaul.

I’ll refrain from posting pictures and details of the cleaning process since there’s really not much to it: Cleaned the PCBs with Isopropyl, completely disassembled the case and pedal and degreased it with hot water and soap,  LIGHTLY lubricated the shaft with car motor oil and that was it. Now, for the LED:

After a quick look at the small PCB where the LED is placed I found a Zener diode in series with the LED and somehow got suspicious about that fellow:

 I went on to search the web for reports about the same problem and, although I found none, I managed to find the circuit schematic here:

Here's the important part for this case:

I suppose BOSS designers put the Zener there so the LED could double both as a status indicator for the effect AND as a battery charge indicator. I’ll try to explain:
Zener diodes act upon electrical flow the same way spring loaded valves act upon water: They only let the flow through if a preset pressure (voltage) builds up upstream of them. So, as the Zener only lets electricity pass through it if the voltage rises above its preset point, the LED will only light up if the battery is able to provide a certain voltage. This way BOSS ensures that the user is made aware that the battery is getting low on charge but the pedal keeps on running for a while because the Zener diode is only in series with the LED. Think of this system as the reserve light on your car’s fuel gauge:
When it lights up you’re still good to go, but you have been warned that it won’t last much longer.

As this, if this Zener is malfunctioning it will affect the indicator LED:

-          If the Zener is shorted the “warning” effect is lost and the LED will keep lit for far longer into the end of the battery’s life
-          If the Zener is open (or if its Zener voltage is somehow out of spec) the LED will not light up at all or will show an erratic behaviour

One good way to check if a Zener diode is doing what it is supposed to do (in simple regulator circuits such as these) is to measure the voltage between a point immediately downstream of it and ground and between a point immediately upstream of it and ground. If the voltage upstream equals the voltage downstream the Zener is shorted. If the voltage downstream is 0 the Zener is open.
In my case the downstream voltage read 1.3V so, although not completely open, the Zener obviously was not letting enough juice through to power the LED.

Since this pedal is to be kept in a pedal board powered by an external supply and there’s no need for low battery warnings, I simply put a jumper across the zener diode D4 to solve the problem:

Now the pedal works perfectly and the LED lights up and shuts down as it is supposed to:

If a more “professional” solution was desired I could have simply replaced the Zener by a new one (any 5.6V Zener would do) and the pedal would have been restored to its original condition.

This fix should be OK for all pedals that use similar circuitry.


Pedro , from Portugal.

sábado, 4 de janeiro de 2014

A new chipamp project part II- A simple DIY guitar power amplifier

 ...for use with an external speaker and some sort of line level preamp (for example, a Behringer VAMP3)

still on a very initial stage (little more that the marine ply box done)