Rank: Member
Groups: Member
Joined: 2/26/2009(UTC)
Posts: 21
Location: Cambridge
|
Hi there,
I noticed that you guys recommend a 470uF filter capacitor for use with the 7805 on the relay driver board. I thought this seemed too low so can I check if it's a typo or not (was it meant to be 4700uF)? If not, then what is the current draw for two relay boards in a ballanced system?
Thanks a lot.
|
|
|
|
|
|
Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA
Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
|
Que? I actually ship 220uF in the kit... 470uF is fine. Relay coils are not that picky. Edited by user Monday, June 15, 2009 9:32:37 AM(UTC)
| Reason: Not specified
|
|
|
|
|
|
Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
|
And it regulated prior to them. :)
|
|
|
|
|
|
Rank: Member
Groups: Member
Joined: 2/26/2009(UTC)
Posts: 21
Location: Cambridge
|
So what voltage are you feeding in? All the calcs/estimates I've done so far suggest that the reg will either drop out or run too hot. With two relay boards I calculated a full load current of 352mA. Add in the remaining components and you're looking at about 500mA aren't you? With only a 220uF capacitor won't you have massive ripple? Maybe my calcs are off but I'd like to understand. Cheers. [Edit: maybe I should give some values. I was planning on using a 15VA transformer with 9V secondaries and a secondary current of 0.83A. ] Edited by user Monday, June 15, 2009 9:47:25 AM(UTC)
| Reason: Not specified
|
|
|
|
|
|
Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
|
In practice it works just fine. :)
The ripple before the reg is actually not that important in this case.
If I were driving more than 2 relays boards I would probably make that cap 1000uf.
Cheers
Russ
|
|
|
|
|
|
Forum Jump
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.
