If you remember Voltlog #117 in that video we analysed some ebay Bussmann fuses to try and figure out if they are fake or real fuses. The ebay fuses we’re way cheaper than anywhere else so that made me suspect they are not genuine.
It’s good to know if the ebay fuses are real or not because they are selling allot of them and people might be relying on these to perform as required when in fact they might be out of spec. For the average bench user which only occasionally goes up to 240VAC it might not be an issue if the fuse is slightly outside the specs but if you are probing some high energy circuit and relying on the ebay fuse to perform according to the datasheet at it is not then something serious might happen, like the multimeter could explode because of a high energy discharge or it could simply damage the meter which is to be avoided.
Links for the products and test equipment shown in this video:
Welcome to a new voltlog, today we are building a very simple constant current regulator based on the LM338 linear regulator. This is a very robust and stable classical regulator that is being manufactured by many big names like ST and TI, it has quite a high output current rating of 5A continuous, it even comes in a TO-3 can package but today we’re going to use a TO220 which is more commonly available.
To make a constant current regulator out of this, is very simple, the datasheet gives us the circuit we need to use and we only need a low value resistor to do that plus the optional input bypassing cap which is 0.1uF. We’re going to use this formula to calculate the value of the resistor, so the output current is equal to the Vref divided by the value of the resistor.
So I discovered this module a few months ago and it’s been sitting in a box since then, I almost forgot about it, until a few days ago when I decided it will be a good idea to do a video on the subject.
Let me give you a few details on the specs of this module and as usual it’s pretty difficult to find the information as it’s the case with every new module coming out of China. First of all we have an input range of 0-60V and 0-10A and a 5V rail is needed to power the module itself. It has a voltage measuring accuracy of ±0.2% + 0.2% full scale which sounds strange because these figures are usually given in a percentage plus or minus a number of least significant digits. The current measuring accuracy is ±0.4% + 0.3% full scale.
The meter is basically capable of measuring with a resolution of 1mv and 1mA (however the accuracy is quite bad, as shown in the video) which is quite nice and useful (not really useful with bad accuracy) for projects like DIY power supplies or DIY electronic loads. It can also display the power in watts with a resolution of 1mW as well as showing the load impedance.