Note de ce sujet :
  • Moyenne : 0 (0 vote(s))
  • 1
  • 2
  • 3
  • 4
  • 5
Attempt at cheap homemade version of Harmony
#61
I didn’t now about UBECs, seems like the way to go. The servo is under enough stress as it is without being driven beyond its rating, much as I would like the extra torque. I currently only use the 5V supply for the servo, could put a USB socket on it for phone charging but haven’t. Some very good little modules available for that purpose if I wanted to add it later.

Interestingly with my average speed over the past 450 miles the lipo battery voltage is settling around 11.3V or about 40%. Of course this means more than half the lipos capacity is unused and so is unnecessary extra weight.
- Oran
Répondre
#62
I swapped all the small package 5 volt voltage regulator on my quadcopter ( Fairchild 7805 or 78M05) to some 99 cents Switching regulator. I don't mind the added weight and they can output 2 amp.  I added an heatsink on one and gave 4 amp @ 70C for educationnal purpose with the kid, well actually more me than the kids. On 12volt they have roughly 80% efficiency going down to 70% on 24 volt. You need to supply only 1 volt above the wanted output.

you can add a diode on the output but you will have a drop of .7volt. Can't recall if they already have one.

This is the product I bought :AKA UBEC

Wish it will be helpful on any circumstance...

Normand is right for the servo don't go above 6 volt. I am still on analog servo, don't know for the digital ones. If they are stated High Voltage servo they can go to 7.4 volt (confimation needed)

Add Capacitor if needed and set the voltage before you connect it to the devices. They are step down LDO switching power supply only.


Used for my 1 meter wingspan plane, it drives two 6 grams servo. No rudder. Blush

[Image: sDrP3tm.jpg]
Avant de le savoir, je l'ignorais...
(antequam sciat ego nescibam)
-  watageek
Répondre
#63
LM7805 are super stable, but sooooo unefficient! Can't believe they still put them on modern RC stuff... They tend to heat up so much that they end up messing with the servo signal when the chip overheats... For flying stuff, it means a crash! Also, When there is a much larger load on the battery (ie. motors), the 7805 starves current and servos/receiver have issues.
-
Si ça a déjà été fait, je peux le faire
Si ça n'a jamais été fait, donnez-moi juste le temps de trouver comment !


Répondre
#64
(09-14-2017, 12:14 AM)Normand_Nadon a écrit : LM7805 are super stable, but sooooo unefficient! Can't believe they still put them on modern RC stuff... They tend to heat up so much that they end up messing with the servo signal when the chip overheats... For flying stuff, it means a crash! Also, When there is a much larger load on the battery (ie. motors), the 7805 starves current and servos/receiver have issues.

Actually they are perfect for a low consumption device where efficiency is not a concern. Super Cheap in a Super small package and self protected for overload and heat... You can even add an big PCB with vias (or a heatsink) to compensate for a bad design . Truly awesome in that aspect.

An oscilloscope can be handy to know the capacitor needed on the LDO output. I put some big low ESR just to be sure because I don't have an oscilloscope and my setup can see some high and low spike since it uses regenerative braking with a high speed brushless.
Avant de le savoir, je l'ignorais...
(antequam sciat ego nescibam)
-  watageek
Répondre


Atteindre :


Utilisateur(s) parcourant ce sujet : 1 visiteur(s)