question
in [Basics]
|
Prev: alluminum block
Next: Soldering with essential tremor
From: Tom Biasi on 16 Jan 2010 12:52 "HF_ATL" <concorde93(a)n_o_s_p_a_m.gmail.com> wrote in message news:LcWdnRbmd6UdQszWnZ2dnUVZ_qWdnZ2d(a)giganews.com... > >HF_ATL wrote: >>> Let's suppose I buy a receiver that has the following information: >>> >>> - Voltage: 7-12V DC (positive center pin) >>> - Output Current: 245 mA >>> >>> but I have a transformer that has 12v DC output (regulated between 1.5 > and >>> 12V) and 500ma, 6VA max, Input 230v-50hz 12.5W. Can I use it to power > the >>> receiver safely? >>> >>> >>> Thanks >>> >>> >>Yes. >> >> Actually, you're right on target. >> >> Its good to operate at 50% capabilities. >> >> >> > > So it means that the transformer gives 500ma maximum but if the receiver > only needs 245ma then only 245ma will be drained by the transformer, > right? > > By the way, it's better to use 9v in the transformer? Since in this case I > have 33,33% and 22,22% respectively for upper and lower voltage limit of > operation of the receiver (7-12V dc)? > > Thanks for your answers! > Your receiver will draw the current necessary from your supply. You have a good margine of safety. The spec of 7-12 volts indicates that the receiver has it's own regulator. Without seeing the circuit I don't know if it would be better to use 9 volts. Even it would, it would matter very little in this case. Tom
From: John Fields on 16 Jan 2010 13:48 On Sat, 16 Jan 2010 08:05:38 -0600, "HF_ATL" <concorde93(a)gmail.com> wrote: >Let's suppose I buy a receiver that has the following information: > >- Voltage: 7-12V DC (positive center pin) >- Output Current: 245 mA > >but I have a transformer that has 12v DC output (regulated between 1.5 and >12V) and 500ma, 6VA max, Input 230v-50hz 12.5W. Can I use it to power the >receiver safely? --- This is sci.electronics.basics so, since you've made a few errors which no one has addressed yet, let's correct them: 1. A receiver doesn't usually have an output current specification, so what you probably mean is that it's rated for 7 to 12VDC in at 245mA max, yes? 2. Transformers don't have DC outputs, so what you're referring to is an AC to DC converter with a regulated output adjustable from 1.5 to 12VDC at 500mA max. 3. It appears you have the input and output spec's somewhat scrambled in that AC inputs are rated in volt-amperes (VA) instead of watts, and output power is rated in watts (W) instead of VA. Such being the case, it appears that your supply requires an input of 230V 50Hz at 12.5VA and can output from 1.5 to 12VDC at 6W max. Notice that this output power can only be realized when the output is set at 12VDC, since with an output voltage >= 1.5V and <12V, the product of voltage and current, which is power, will always be less than 6 watts. All that aside, since your supply can deliver 12VDC at 500mA and your receiver only needs 245mA at 12V, it'll work fine with the supply set at 12V, as other posters have stated. JF
From: Paul E. Schoen on 16 Jan 2010 14:11 "John Fields" <jfields(a)austininstruments.com> wrote in message news:7014l5t0i3rpr56971d0na9l6krfbu1jeh(a)4ax.com... > On Sat, 16 Jan 2010 08:05:38 -0600, "HF_ATL" <concorde93(a)gmail.com> > wrote: > >>Let's suppose I buy a receiver that has the following information: >> >>- Voltage: 7-12V DC (positive center pin) >>- Output Current: 245 mA >> >>but I have a transformer that has 12v DC output (regulated between 1.5 >>and >>12V) and 500ma, 6VA max, Input 230v-50hz 12.5W. Can I use it to power the >>receiver safely? > > --- > This is sci.electronics.basics so, since you've made a few errors which > no one has addressed yet, let's correct them: > > 1. A receiver doesn't usually have an output current specification, so > what you probably mean is that it's rated for 7 to 12VDC in at 245mA > max, yes? > > 2. Transformers don't have DC outputs, so what you're referring to is an > AC to DC converter with a regulated output adjustable from 1.5 to > 12VDC at 500mA max. > > 3. It appears you have the input and output spec's somewhat scrambled in > that AC inputs are rated in volt-amperes (VA) instead of watts, and > output power is rated in watts (W) instead of VA. > > Such being the case, it appears that your supply requires an input of > 230V 50Hz at 12.5VA and can output from 1.5 to 12VDC at 6W max. > > Notice that this output power can only be realized when the output is > set at 12VDC, since with an output voltage >= 1.5V and <12V, the > product of voltage and current, which is power, will always be less > than 6 watts. > > All that aside, since your supply can deliver 12VDC at 500mA and your > receiver only needs 245mA at 12V, it'll work fine with the supply set at > 12V, as other posters have stated. If the adjustable supply is a switcher, or if it uses a selection of taps on a transformer, AND if the receiver has a linear regulator which accepts the 7-12 VDC, then better overall efficiency may be obtained by setting the supply to a lower value. You save (12-9)*0.245 = 0.74 watts by using 9 VDC. Go for the green energy star! Paul
From: HF_ATL on 16 Jan 2010 14:52 > >"John Fields" <jfields(a)austininstruments.com> wrote in message >news:7014l5t0i3rpr56971d0na9l6krfbu1jeh(a)4ax.com... >> On Sat, 16 Jan 2010 08:05:38 -0600, "HF_ATL" <concorde93(a)gmail.com> >> wrote: >> >>>Let's suppose I buy a receiver that has the following information: >>> >>>- Voltage: 7-12V DC (positive center pin) >>>- Output Current: 245 mA >>> >>>but I have a transformer that has 12v DC output (regulated between 1.5 >>>and >>>12V) and 500ma, 6VA max, Input 230v-50hz 12.5W. Can I use it to power the >>>receiver safely? >> >> --- >> This is sci.electronics.basics so, since you've made a few errors which >> no one has addressed yet, let's correct them: >> >> 1. A receiver doesn't usually have an output current specification, so >> what you probably mean is that it's rated for 7 to 12VDC in at 245mA >> max, yes? >> >> 2. Transformers don't have DC outputs, so what you're referring to is an >> AC to DC converter with a regulated output adjustable from 1.5 to >> 12VDC at 500mA max. >> >> 3. It appears you have the input and output spec's somewhat scrambled in >> that AC inputs are rated in volt-amperes (VA) instead of watts, and >> output power is rated in watts (W) instead of VA. >> >> Such being the case, it appears that your supply requires an input of >> 230V 50Hz at 12.5VA and can output from 1.5 to 12VDC at 6W max. >> >> Notice that this output power can only be realized when the output is >> set at 12VDC, since with an output voltage >= 1.5V and <12V, the >> product of voltage and current, which is power, will always be less >> than 6 watts. >> >> All that aside, since your supply can deliver 12VDC at 500mA and your >> receiver only needs 245mA at 12V, it'll work fine with the supply set at >> 12V, as other posters have stated. > >If the adjustable supply is a switcher, or if it uses a selection of taps >on a transformer, AND if the receiver has a linear regulator which accepts >the 7-12 VDC, then better overall efficiency may be obtained by setting the >supply to a lower value. You save (12-9)*0.245 = 0.74 watts by using 9 VDC. > >Go for the green energy star! > >Paul > > Thanks all of you for the feedback. So, right now I have no doubts that I can use the power adapter. This is the item I want to buy: http://alai.h3m.com/~s0350672/catalogo/product_info.php?products_id=441&osCsid=d32035323c73bc5e61f72e5430e3891f Don't know if the receiver has a linear regulator or not, only know what's described in the website. Btw, for 72 euros considering a 200mw 1.2ghz transmitter + receiver, is a expensive set? Thanks again! --------------------------------------- This message was sent using the sci.electronics.basics web interface on http://www.Electronics-Related.com
From: Jasen Betts on 17 Jan 2010 14:21
On 2010-01-16, HF_ATL <concorde93(a)gmail.com> wrote: > Let's suppose I buy a receiver that has the following information: > > - Voltage: 7-12V DC (positive center pin) > - Output Current: 245 mA > > but I have a transformer that has 12v DC output (regulated between 1.5 and > 12V) and 500ma, 6VA max, Input 230v-50hz 12.5W. Can I use it to power the > receiver safely? given that it's regulated yeah that'll work (as long as you get + on the center pin) If it's adjustable I'de b incluned to set it to 9V or 7.5V just for extra safety. --- news://freenews.netfront.net/ - complaints: news(a)netfront.net --- |