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1KHz signal generator with a 555 timer

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555-ic-astable-1000hz.asc

555 IC Formulas

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## Astable waveforms

Charge time (output high)

t1 = 0.693(Ra+Rb)C

Discharge time (output low)

t2 = 0.693(Rb)C

Total period

T = t1+t2 = 0.693(Ra+2Rb)C

Frequency of oscillation

f = 1/T = 1.44/(Ra+2Rb)C

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Configuring a SAML IDP with LDAP as authentication source

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In this setup, the SAML IDP will be available at example.com/auth and we will use the ldap server configured in this post.

Start by moving to the directory above the DocumentRoot for the domain. Let’s say that it is /var/www/example.com, so

cd /var/www/

Download the latest simplesamlphp version

wget https://simplesamlphp.org/res/downloads/simplesamlphp-1.14.4.tar.gz && tar xvfz simplesamlphp-1.14.4.tar.gz

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Installing and configuring LDAP and phpldapadmin

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This will be a minimal setup. It’s a good idea to start by doing an update and upgrade on your system. In debian, use:

apt-get update && apt-get upgrade

Install the packages (set and confirm admin password)

apt-get install slapd ldap-utils phpldapadmin

Then vim /etc/ldap/ldap.conf and include:

BASE dc=example,dc=net
URI ldap://127.0.0.1

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Quick proxy script for sharing internet among devices

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I created this script to automatize sharing of the hotspot connection I’m using.

Scenario:
My laptop is connected to the hotspot wifi. This internet connection will be shared to a router via an ethernet cable (which is also plugged to the laptop). The router then will distribute the connection to multiple devices.

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Docker guide

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Install docker (you may need to reboot afterwards)

pacman -S docker

Start docker

systemctl start docker

Check docker information

docker info

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Debugging your car’s battery and alternator with a multimeter

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Attention:

In order to minimize eventual residual surface charges, consider to leave the radio or headlights on for a couple of minutes prior to the measurement procedure.

Procedure:

1. Set your multimeter to DCV and select a range at least above 15V.
2. Connect the multimeter leads (black is ground) to the battery. The optimal reading is around 12.6V.
3. Now start the car with the multimeter connected to the battery. Voltage should not drop lower than 10V (it’s ok to drop to 11V).
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