Hi Graham & Michael,
Ref: "you could substitute a horn, pump or radar rotation motor."
Michael; Don't get too enthusiastic with the loads / functions you want to switch !
Your Switcher is a very tiny device and, as suspected; looking at the description and, rather sparse, manual on the Mtroniks site
it seems that the switched outputs are limited to 50mA !!
Presumably direct from the logic IC outputs with no output driver stage due to the small package.
Thus if you want to use it for a higher load, e.g. a radar motor, you would need to put a relay or switching transistor, with associated transistor driver, in between.
Bit of a faff about if you ask me (which some still do😉) since there are higher power switchers on the market - have a look at Component Shop Action Electronics range.
The 'manual' BTW is seemingly daft, everything repeated in four columns and UPSIDE DOWN on the website?? 🙄
Since the total load current capability of this switcher is only 100mA I can't see any need for a separate battery. A half decent RX battery or BEC will hardly notice an extra 100mA. I typically use a 4.8 or 6V NiMh battery depending on the RX specs. Or in simple installations, i.e. just rudder servo and ESC, I let the BEC of the ESC take the strain.
So, with 50mA per output what can you do?
(Graham93, Dave976 (alias M) and similar members, can switch off here, as this is 'old hat' for them!😉)
A. Two 25mA LEDs in parallel. Each LED sipping 25mA. (0.025A) x 2 = 0.05A
Dropping resistor for each LED: Given an RX battery voltage of 5V and Vf of 2.5V-
R=(Vs-Vf)/0.025. or 2.5/0.025 = 100 Ohms. Which luckily happens one of the commonly available so called 'preferred values' 😀
Vs = battery voltage,
Vf = forward voltage drop of the LED., i.e. voltage at which it 'strikes' and lights up. Vf varies from ~2.0 to 3.0V but in my experience taking an average value of 2.5V is good enough.
B. Using a separate battery: any number of LEDs of up to 50mA current draw in series, as long as your battery is of high enough voltage.
Typical current would be 20 -30mA and in my experience taking a 25mA average will do nicely without any significant variation in brilliance.
Formula: Vs=> VfxN. N = number of LEDs in the series chain.
If your Vs is more than VfxN then you will need a dropping resistor to limit the current to ~25mA.
Formula: R (ohms) = (Vs - (VfxN))/I
E.g. Given a battery voltage of 12V and Vf of 2.5V and 4 LEDs-
R = (12-10)/0.025 ---> 80 Ohms.
Given the switcher max current of 50mA it should handle two such '25mA chains in parallel.
BTW: Much has been made on this site (and others) of the need for different resistors for LEDs of different colours, in my experience, and experimentation with standard 3mm, 5mm and SMD LEDs, the average values given above can be used with impunity.
NOTE: If using special hi-power/hi-brightness LEDs other values may apply! Check the specs!!
Hope this helps a little to demystify and simplify things.
Cheers, Doug 😎
PS to Graham: I can't see what purpose Jacko's extra diodes should serve either.